Thyroid Function in Early Pregnancy, Child IQ, and Autistic Traits: A Meta-Analysis of Individual Participant Data

Development of an animal model of hypothyroxinemia during pregnancy in Wistar rats

BACKGROUND

Hypothyroxinemia is a subclinical thyroid hormone deficiency in which the mother has inadequate levels of T4 during pregnancy. The fetus relies entirely on the mother's T4 hormone level for early neurodevelopment. Isolated maternal hypothyroxinemia (IMH) in the first trimester of pregnancy can lead to lower intelligence, lower motor scores, and a higher risk of mental illness in descendants. Here, we focus on the autism-like behavior of IMH offspring.

METHODS

The animals were administered 1 ppm of propylthiouracil (PTU) for 9 weeks. Then, the concentrations of T3, T4, and thyroid-stimulating hormone (TSH) were detected using enzyme-linked immunosorbent assay (ELISA) to verify the developed animal model of IMH. We performed four behavioral experiments, including the marble burying test, open-field test, three-chamber sociability test, and Morris water maze, to explore the autistic-like behavior of 40-day-old offspring rats.

RESULTS

The ELISA test showed that the serum T3 and TSH concentrations in the model group were normal compared with the negative control group, whereas the T4 concentration decreased. In the behavioral experiments, the number of hidden marbles in the offspring of IMH increased significantly, the frequency of entering the central compartment decreased, and the social ratio decreased significantly.

CONCLUSION

The animal model of IMH was developed by the administration of 1 ppm of PTU for 9 weeks, and there were autistic-like behavior changes such as anxiety, weakened social ability, and repeated stereotyping in the IMH offspring by 40 days.

Gestational hypothyroxinemia induces ASD-like phenotypes in behavior, proinflammatory markers, and glutamatergic protein expression in mouse offspring of both sexes

Background

The prevalence of autism spectrum disorder (ASD) has significantly risen in the past three decades, prompting researchers to explore the potential contributions of environmental factors during pregnancy to ASD development. One such factor of interest is gestational hypothyroxinemia (HTX), a frequent condition in pregnancy associated with cognitive impairments in the offspring. While retrospective human studies have linked gestational HTX to autistic traits, the cellular and molecular mechanisms underlying the development of ASD-like phenotypes remain poorly understood. This study used a mouse model of gestational HTX to evaluate ASD-like phenotypes in the offspring.

Methods

To induce gestational HTX, pregnant mice were treated with 2-mercapto-1-methylimidazole (MMI), a thyroid hormones synthesis inhibitor, in the tap-drinking water from embryonic days (E) 10 to E14. A separate group received MMI along with a daily subcutaneous injection of T4, while the control group received regular tap water during the entire pregnancy. Female and male offspring underwent assessments for repetitive, anxious, and social behaviors from postnatal day (P) 55 to P64. On P65, mice were euthanized for the evaluation of ASD-related inflammatory markers in blood, spleen, and specific brain regions. Additionally, the expression of glutamatergic proteins (NLGN3 and HOMER1) was analyzed in the prefrontal cortex and hippocampus.

Results

The HTX-offspring exhibited anxious-like behavior, a subordinate state, and impaired social interactions. Subsequently, both female and male HTX-offspring displayed elevated proinflammatory cytokines in blood, including IL-1β, IL-6, IL-17A, and TNF-α, while only males showed reduced levels of IL-10. The spleen of HTX-offspring of both sexes showed increased Th17/Treg ratio and M1-like macrophages. In the prefrontal cortex and hippocampus of male HTX-offspring, elevated levels of IL-17A and reduced IL-10 were observed, accompanied by increased expression of hippocampal NLGN3 and HOMER1. All these observations were compared to those observed in the Control-offspring. Notably, the supplementation with T4 during the MMI treatment prevents the development of the observed phenotypes. Correlation analysis revealed an association between maternal T4 levels and specific ASD-like outcomes.

Discussion

This study validates human observations, demonstrating for the first time that gestational HTX induces ASD-like phenotypes in the offspring, highlighting the need of monitoring thyroid function during pregnancy.

The research landscape concerning environmental factors in neurodevelopmental disorders: Endocrine disrupters and pesticides-A review

In recent years, environmental epidemiology and toxicology have seen a growing interest in the environmental factors that contribute to the increased prevalence of neurodevelopmental disorders, with the purpose of establishing appropriate prevention strategies. A literature review was performed, and 192 articles covering the topic of endocrine disruptors and neurodevelopmental disorders were found, focusing on polychlorinated biphenyls, polybrominated diphenyl ethers, bisphenol A, and pesticides. This study contributes to analyzing their effect on the molecular mechanism in maternal and infant thyroid function, essential for infant neurodevelopment, and whose alteration has been associated with various neurodevelopmental disorders. The results provide scientific evidence of the association that exists between the environmental neurotoxins and various neurodevelopmental disorders. In addition, other possible molecular mechanisms by which pesticides and endocrine disruptors may be associated with neurodevelopmental disorders are being discussed.

Gestational thyroid hormones and autism-related traits in the EARLI and HOME studies

Thyroid hormones are essential for neurodevelopment. Few studies have considered associations with quantitatively measured autism spectrum disorder (ASD)-related traits, which may help elucidate associations for a broader population. Participants were drawn from two prospective pregnancy cohorts: the Early Autism Risk Longitudinal Investigation (EARLI), enrolling pregnant women who already had a child with ASD, and the Health Outcomes and Measures of the Environment (HOME) Study, following pregnant women from the greater Cincinnati, OH area. Gestational thyroid-stimulating hormone (TSH) and free thyroxine (FT4) were measured in mid-pregnancy 16 (±3) weeks gestation serum samples. ASD-related traits were measured using the Social Responsiveness Scale (SRS) at ages 3-8 years. The association was examined using quantile regression, adjusting for maternal and sociodemographic factors. 278 participants (132 from EARLI, 146 from HOME) were included. TSH distributions were similar across cohorts, while FT4 levels were higher in EARLI compared to HOME. In pooled analyses, particularly for those in the highest SRS quantile (95th percentile), higher FT4 levels were associated with increasing SRS scores (β = 5.21, 95% CI = 0.93, 9.48), and higher TSH levels were associated with decreasing SRS scores (β = -6.94, 95% CI = -11.04, -2.83). The association between TSH and SRS remained significant in HOME for the 95% percentile of SRS scores (β = -6.48, 95% CI = -12.16, -0.80), but not EARLI. Results for FT4 were attenuated when examined in the individual cohorts. Our results add to evidence that gestational thyroid hormones may be associated with ASD-related outcomes by suggesting that relationships may differ across the distribution of ASD-related traits and by familial likelihood of ASD.

Emerging research themes in maternal hypothyroidism: a bibliometric exploration

Background

Hypothyroidism, a prevalent endocrine disorder, carries significant implications for maternal and infant health, especially in the context of maternal hypothyroidism. Despite a gradual surge in recent research, achieving a comprehensive understanding of the current state, focal points, and developmental trends in this field remains challenging. Clarifying these aspects and advancing research could notably enhance maternal-infant health outcomes. Therefore, this study employs bibliometric methods to systematically scrutinize maternal hypothyroidism research, serving as a reference for further investigations.

Objective

Through bibliometric analysis, this study seeks to unveil key research focus areas, developmental trends, and primary contributors in Maternal Hypothyroidism. The findings offer insights and recommendations to inform future research endeavors in this domain.

Methods

Literature metrics analysis was performed on data retrieved and extracted from the Web of Science Core Collection database. The analysis examined the evolution and thematic trends of literature related to Maternal Hypothyroidism. Data were collected on October 28, 2023, and bibliometric analysis was performed using VOSviewer, CiteSpace, and the Bibliometrix software package, considering specific characteristics such as publication year, country/region, institution, authorship, journals, references, and keywords.

Results

Retrieved from 1,078 journals, 4,184 articles were authored by 18,037 contributors in 4,580 institutions across 113 countries/regions on six continents. Maternal Hypothyroidism research publications surged from 44 to 310 annually, a 604.54% growth from 1991 to 2022. The USA (940 articles, 45,233 citations), China Medical University (82 articles, 2,176 citations), and Teng, Weiping (52 articles, 1,347 citations) emerged as the most productive country, institution, and author, respectively. "Thyroid" topped with 233 publications, followed by "Journal of Clinical Endocrinology & Metabolism" (202) with the most citations (18,513). "Pregnancy" was the most cited keyword, with recent high-frequency keywords such as "outcome," "gestational diabetes," "iodine intake," "preterm birth," "guideline," and "diagnosis" signaling emerging themes in Maternal Hypothyroidism.

Conclusions

This study unveils developmental trends, global collaboration patterns, foundational knowledge, and emerging frontiers in Maternal Hypothyroidism. Over 30 years, research has predominantly focused on aspects like diagnosis, treatment guidelines, thyroid function during pregnancy, and postpartum outcomes, with a central emphasis on the correlation between maternal and fetal health.

Lack of beneficiary effect of levothyroxine therapy of pregnant women with subclinical hypothyroidism in terms of neurodevelopment of their offspring

PURPOSE

Despite the beneficial effects of levothyroxine (LT4) therapy on pregnancy outcomes of women with subclinical hypothyroidism (SCH), its impact on the developmental status of offspring remains unclear. We aimed to assess the effects of LT4 therapy on the neurodevelopment of infants of SCH women in the first 3 years of life.

METHODS

A follow-up study was conducted on children born to SCH pregnant women who had participated in a single-blind randomized clinical trial (Tehran Thyroid and Pregnancy Study). In this follow-up study, 357 children of SCH mothers were randomly assigned to SCH + LT4 (treated with LT4 after the first prenatal visit and throughout pregnancy) and SCH-LT4 groups. Children born of euthyroid TPOAb-women served as the control group (n = 737). The neurodevelopment status of children was assessed in five domains (communication, gross motor, fine motor, problem-solving, and social-personal domains) using the Ages and Stages Questionnaires (ASQ) at the age of 3 years.

RESULTS

Pairwise comparisons of ASQ domains between euthyroid, SCH + LT4, and SCH-LT4 groups show no statistically significant difference between groups in the total score [median 25-75 total score: 265 (240-280); 270 (245-285); and 265 (245-285); P-value = 0.2, respectively]. The reanalyzing data using the TSH cutoff value of 4.0 mIU/L indicated no significant difference between groups in the score of ASQ in each domain or total score with TSH levels < 4.0 mIU/L, however, a statistically significant difference in the median score of the gross motor was observed between those SCH + LT4 with baseline TSH values ≥ 4.0 mIU/L and SCH-LT4 [60 (55-60) vs. 57.5 (50-60); P = 0.01].

CONCLUSIONS

Our study does not support the beneficiary effect of LT4 therapy for SCH pregnant women in terms of the neurological development of their offspring in the first three years of life.

Endocrine Disruptors and Thyroid Health

A wide variety of thyroidal endocrine-disrupting chemicals (EDCs) have been identified. Exposure to known thyroidal EDCs is ubiquitous, and many likely remain unidentified. The sources of exposure include contaminated drinking water, air pollution, pesticides and agricultural chemicals, flame retardants, cleaning supplies, personal care products, food additives and packaging materials, coatings and solvents, and medical products and equipment. EDCs can affect thyroid hormone synthesis, transport, metabolism, and action in a myriad of ways. Understanding the health effects of thyroidal EDCs has been challenging because individuals may have multiple concomitant EDC exposures and many potential EDCs are not yet well characterized. Because of the importance of thyroid hormone for brain development in early life, pregnant women and young infants are particularly vulnerable to the effects of environmental thyroid disruption. The thyroidal effects of some EDCs may be exacerbated in iodine-deficient individuals, those with thyroid autoimmunity, and those with mutations in deiodinase genes. Differential exposures to EDCs may exacerbate health disparities in disadvantaged groups. High-throughput in vitro assays and in silico methods and methods that can detect the effects of relevant EDC mixtures are needed. In addition, optimal methods for detecting the effects of thyroidal EDCs on neurodevelopment need to be developed. Common sense precautions can reduce some thyroidal EDC exposures; however, regulation of manufacturing and drinking water content will ultimately be needed to protect populations.

Fluoride exposure and thyroid hormone levels in pregnancy: The MIREC cohort

BACKGROUND

Fluoride exposure may increase the risk of hypothyroidism, but results from previous studies are inconsistent at low-level fluoride exposure (i.e., ≤0.7 mg/L). Human studies of fluoride and thyroid hormone levels in pregnancy are scarce.

OBJECTIVES

We examined associations between fluoride exposure and maternal thyroid hormone levels in a Canadian pregnancy cohort, with consideration for fetal sex-specific effects.

METHODS

We measured fluoride concentrations in drinking water and spot urine samples collected during each trimester from 1876 pregnant women enrolled in the Maternal-Infant Research on Environmental Chemicals (MIREC) study. We also measured maternal thyroid stimulating hormone (TSH), free thyroxine (FT4), and total thyroxine (TT4) levels during the first trimester of pregnancy. We used linear and non-linear regression models to estimate associations between fluoride exposure and levels of TSH, FT4, and TT4. We explored effect modification by fetal sex and considered maternal iodine status as a potential confounder.

RESULTS

A 1 mg/L increase in urinary fluoride was associated with a 0.30 (95 %CI: 0.08, 0.51) logarithmic unit (i.e., 35.0 %) increase in TSH among women pregnant with females, but not males (B = 0.02; 95 %CI: -0.16, 0.19). Relative to women with urinary fluoride concentrations in the first quartile (0.05-0.32 mg/L), those with levels in the third quartile (0.49-0.75 mg/L) had higher FT4 and TT4 (i.e., inverted J-shaped associations), but the association was not statistically significant after adjustment for covariates (p = 0.06). Water fluoride concentration showed a U-shaped association with maternal FT4, whereby women with water fluoride concentrations in the second (0.13-0.52 mg/L) and third (0.52-0.62 mg/L) quartiles had significantly lower FT4 compared to those with levels in the first quartile (0.04-0.13 mg/L). Adjustment for maternal iodine status did not change the results.

DISCUSSION

Fluoride exposure was associated with alterations in maternal thyroid hormone levels, the magnitude of which appeared to vary by fetal sex. Given the importance of maternal thyroid hormones for fetal neurodevelopment, replication of findings is warranted.

Maternal Thyroid Dysfunction During Pregnancy as an Etiologic Factor in Autism Spectrum Disorder: Challenges and Opportunities for Research

Background: Autism spectrum disorder (ASD) is a neurodevelopmental condition with unknown etiology. Both genetic and environmental factors have been associated with ASD. Environmental exposures during the prenatal period may play an important role in ASD development. This narrative review critically examines the evidence for a relationship between maternal thyroid dysfunction during pregnancy and ASD in the child. Summary: Studies that assessed the associations of hypothyroidism, hyperthyroidism, hypothyroxinemia, thyroid hormone concentrations, or autoimmune thyroid disease with ASD outcomes were included. Most research focused on the relationship between hypothyroidism and ASD. Multiple population-based studies found that maternal hypothyroidism was associated with higher likelihood of an ASD diagnosis in offspring. Associations with other forms of maternal thyroid dysfunction were less consistent. Findings may have been affected by misclassification bias, survival bias, or publication bias. Studies using medical records may have misclassified subclinical thyroid dysfunction as euthyroidism. Two studies that assessed children at early ages may have misclassified those with ASD as typically developing. Most studies adjusted for maternal body mass index (BMI) and/or mental illness, but not interpregnancy interval or pesticide exposure, all factors associated with fetal survival and ASD. Most studies reported a combination of null and statistically significant findings, although publication bias is still possible. Conclusions: Overall, evidence supported a positive association between maternal thyroid dysfunction during pregnancy and ASD outcomes in the child, especially for hypothyroidism. Future studies could reduce misclassification bias by using laboratory measures instead of medical records to ascertain thyroid dysfunction and evaluating children for ASD at an age when it can be reliably detected. Survival bias could be further mitigated by adjusting models for more factors associated with fetal survival and ASD. Additional research is needed to comprehensively understand the roles of maternal levothyroxine treatment, iodine deficiency, or exposure to thyroid-disrupting compounds in the relationship between maternal thyroid dysfunction and child ASD outcomes.

Sleep duration in preschool age and later behavioral and cognitive outcomes: an individual participant data meta-analysis in five European cohorts

Short sleep duration has been linked to adverse behavioral and cognitive outcomes in schoolchildren, but few studies examined this relation in preschoolers. We aimed to investigate the association between parent-reported sleep duration at 3.5 years and behavioral and cognitive outcomes at 5 years in European children. We used harmonized data from five cohorts of the European Union Child Cohort Network: ALSPAC, SWS (UK); EDEN, ELFE (France); INMA (Spain). Associations were estimated through DataSHIELD using adjusted generalized linear regression models fitted separately for each cohort and pooled with random-effects meta-analysis. Behavior was measured with the Strengths and Difficulties Questionnaire. Language and non-verbal intelligence were assessed by the Wechsler Preschool and Primary Scale of Intelligence or the McCarthy Scales of Children's Abilities. Behavioral and cognitive analyses included 11,920 and 2981 children, respectively (34.0%/13.4% of the original sample). In meta-analysis, longer mean sleep duration per day at 3.5 years was associated with lower mean internalizing and externalizing behavior percentile scores at 5 years (adjusted mean difference: - 1.27, 95% CI [- 2.22, - 0.32] / - 2.39, 95% CI [- 3.04, - 1.75]). Sleep duration and language or non-verbal intelligence showed trends of inverse associations, however, with imprecise estimates (adjusted mean difference: - 0.28, 95% CI [- 0.83, 0.27] / - 0.42, 95% CI [- 0.99, 0.15]). This individual participant data meta-analysis suggests that longer sleep duration in preschool age may be important for children's later behavior and highlight the need for larger samples for robust analyses of cognitive outcomes. Findings could be influenced by confounding or reverse causality and require replication.

Gut microbiota short-chain fatty acids and their impact on the host thyroid function and diseases

Thyroid disorders are clinically characterized by alterations of L-3,5,3',5'-tetraiodothyronine (T4), L-3,5,3'-triiodothyronine (T3), and/or thyroid-stimulating hormone (TSH) levels in the blood. The most frequent thyroid disorders are hypothyroidism, hyperthyroidism, and hypothyroxinemia. These conditions affect cell differentiation, function, and metabolism. It has been reported that 40% of the world's population suffers from some type of thyroid disorder and that several factors increase susceptibility to these diseases. Among them are iodine intake, environmental contamination, smoking, certain drugs, and genetic factors. Recently, the intestinal microbiota, composed of more than trillions of microbes, has emerged as a critical player in human health, and dysbiosis has been linked to thyroid diseases. The intestinal microbiota can affect host physiology by producing metabolites derived from dietary fiber, such as short-chain fatty acids (SCFAs). SCFAs have local actions in the intestine and can affect the central nervous system and immune system. Modulation of SCFAs-producing bacteria has also been connected to metabolic diseases, such as obesity and diabetes. In this review, we discuss how alterations in the production of SCFAs due to dysbiosis in patients could be related to thyroid disorders. The studies reviewed here may be of significant interest to endocrinology researchers and medical practitioners.

Iodine Deficiency, Maternal Hypothyroxinemia and Endocrine Disrupters Affecting Fetal Brain Development: A Scoping Review

This scoping review critically discusses the publications of the last 30 years on the impact of mild to moderate iodine deficiency and the additional impact of endocrine disrupters during pregnancy on embryonal/fetal brain development. An asymptomatic mild to moderate iodine deficiency and/or isolated maternal hypothyroxinemia might affect the development of the embryonal/fetal brain. There is sufficient evidence underlining the importance of an adequate iodine supply for all women of childbearing age in order to prevent negative mental and social consequences for their children. An additional threat to the thyroid hormone system is the ubiquitous exposure to endocrine disrupters, which might exacerbate the effects of iodine deficiency in pregnant women on the neurocognitive development of their offspring. Ensuring adequate iodine intake is therefore essential not only for healthy fetal and neonatal development in general, but it might also extenuate the effects of endocrine disruptors. Individual iodine supplementation of women of childbearing age living in areas with mild to moderate iodine deficiency is mandatory as long as worldwide universal salt iodization does not guarantee an adequate iodine supply. There is an urgent need for detailed strategies to identify and reduce exposure to endocrine disrupters according to the "precautional principle".

Fluoride Exposure and ADHD: A Systematic Review of Epidemiological Studies

Background and objectives: Attention deficit hyperactivity disorder (ADHD) is a childhood-onset neurodevelopmental disorder characterized by two dimensions: inattentiveness and hyperactivity/impulsivity. ADHD may be the result of complex interactions between genetic, biological and environmental factors possibly including fluoride exposure. Materials and methods: A literature search was performed on 31 March 2023 in the following databases: PubMed, Embase and Web of Science. We defined the following inclusion criteria according to the PECOS statement: a healthy child and adolescent population (P), fluoride exposure of any type (E), comparison with low or null exposure (C), ADHD spectrum disorder (O), and ecological, cross-sectional, case-control and cohort studies (S). Results: We found eight eligible records corresponding to seven different studies investigating the effect of fluoride exposure on children and adolescents. One study had a cohort design and one a case-control one, while five were cross-sectional. Only three studies applied validated questionnaires for the purpose of ADHD diagnosis. As regards exposure assessment, levels of fluoride in urine and tap water were, respectively used in three and two studies, while two used both. Three studies reported a positive association with ADHD risk, all assessing exposure through fluoride levels. By using urinary fluoride, conversely, a positive correlation with inattention, internalizing symptoms, cognitive and psychosomatic problems was found in three studies, but no relation was found in the other one. Conclusions: The present review suggests that early exposure to fluoride may have neurotoxic effects on neurodevelopment affecting behavioral, cognitive and psychosomatic symptoms related to ADHD diagnosis. However, due to the heterogeneity of the studies included, current evidence does not allow to conclusively confirm that fluoride exposure is specifically linked to ADHD development.

Fluoride exposure and hypothyroidism in a Canadian pregnancy cohort

BACKGROUND

While fluoride can have thyroid-disrupting effects, associations between low-level fluoride exposure and thyroid conditions remain unclear, especially during pregnancy when insufficient thyroid hormones can adversely impact offspring development.

OBJECTIVES

We evaluated associations between fluoride exposure and hypothyroidism in a Canadian pregnancy cohort.

METHODS

We measured fluoride concentrations in drinking water and three dilution-corrected urine samples and estimated fluoride intake based on self-reported beverage consumption. We classified women enrolled in the Maternal-Infant Research on Environmental Chemicals Study as euthyroid (n = 1301), subclinical hypothyroid (n = 100) or primary hypothyroid (n = 107) based on their thyroid hormone levels in trimester one. We used multinomial logistic regression to estimate the association between fluoride exposure and classification of either subclinical or primary hypothyroidism and considered maternal thyroid peroxidase antibody (TPOAb) status, a marker of autoimmune hypothyroidism, as an effect modifier. In a subsample of 466 mother-child pairs, we used linear regression to explore the association between maternal hypothyroidism and child Full-Scale IQ (FSIQ) at ages 3-to-4 years and tested for effect modification by child sex.

RESULTS

A 0.5 mg/L increase in drinking water fluoride concentration was associated with a 1.65 (95 % confidence interval [CI]: 1.04, 2.60) increased odds of primary hypothyroidism. In contrast, we did not find a significant association between urinary fluoride (adjusted odds ratio [aOR]: 1.00; 95%CI: 0.73, 1.39) or fluoride intake (aOR: 1.25; 95%CI: 0.99, 1.57) and hypothyroidism. Among women with normal TPOAb levels, the risk of primary hypothyroidism increased with both increasing water fluoride and fluoride intake (aOR water fluoride concentration: 2.85; 95%CI: 1.25, 6.50; aOR fluoride intake: 1.75; 95%CI: 1.27, 2.41). Children born to women with primary hypothyroidism had lower FSIQ scores compared to children of euthyroid women, especially among boys (B coefficient: -8.42; 95 % CI: -15.33, -1.50).

DISCUSSION

Fluoride in drinking water was associated with increased risk of hypothyroidism in pregnant women. Thyroid disruption may contribute to developmental neurotoxicity of fluoride.

Interaction between isolated maternal hypothyroxinemia and pregnancy-related anxiety on preschooler's internalizing and externalizing problems: A birth cohort study

BACKGROUND

Isolated maternal hypothyroxinemia (IMH) and pregnancy-related anxiety may increase the risk of offspring's emotional and behavioral problems, but little is known about their potential interactive effect on preschoolers' internalizing and externalizing problems.

METHODS

We conducted a large prospective cohort study in Ma'anshan Maternal and Child Health Hospital between May 2013 and September 2014. There were a total of 1372 mother-child pairs from the Ma'anshan birth cohort (MABC) included in this study. IMH was defined as the thyroid-stimulating hormone (TSH) level within the normal reference range (2.5-97.5th percentile) and the free thyroxine (FT₄) level below the 2.5th percentile, and negative TPOAb. The pregnancy-related anxiety questionnaire (PRAQ) was used to assess women's pregnancy-related anxiety status in the first (1-13 weeks), second (14-27 weeks) and third (after 28 weeks) trimesters of pregnancy. The Achenbach Child Behavior Checklist (CBCL/1.5-5) was used to assess preschoolers' internalizing and externalizing problems.

RESULTS

Preschoolers born of mothers with IMH and anxiety had an increased risk of anxious/depressed (OR = 6.40, 95% CI 1.89-21.68), somatic complaints (OR = 2.69, 95% CI 1.01-7.20), attention problems (OR = 2.95, 95% CI 1.00-8.69) and total problems (OR = 3.40, 95% CI 1.60-7.21). Particularly, mothers with IMH and anxiety was associated with an increased risk of preschool girls' anxious/depressed (OR = 8.14, 95% CI 1.74-38.08), withdrawn (OR = 7.03, 95% CI 2.25-21.92), internalizing problems (OR = 2.66, 95% CI 1.00-7.08), and total problems (OR = 5.50, 95% CI 2.00-15.10).

CONCLUSIONS

IMH and pregnancy-related anxiety during pregnancy may synergistically increase the risk of internalizing and externalizing problems in preschooler children. This interaction is distinct in internalizing problems of preschool girls.

Fluoride exposure and cognitive neurodevelopment: Systematic review and dose-response meta-analysis

Many uncertainties still surround the possible harmful effect of fluoride exposure on cognitive neurodevelopment in children. The aim of this systematic review and meta-analysis was to characterize this relation through a dose-response approach, by comparing the intelligence quotient (IQ) scores in the highest versus the lowest fluoride exposure category with a random-effects model, within a one-stage dose-response meta-analysis based on a cubic spline random-effects model. Out of 1996 potentially relevant literature records, 33 studies were eligible for this review, 30 of which were also suitable for meta-analysis. The summary mean difference of IQ score, comparing highest versus lowest fluoride categories and considering all types of exposure, was -4.68 (95% confidence interval-CI -6.45; -2.92), with a value of -5.60 (95% CI -7.76; -3.44) for drinking water fluoride and -3.84 (95% CI -7.93; 0.24) for urinary fluoride. Dose-response analysis showed a substantially linear IQ decrease for increasing water fluoride above 1 mg/L, with -3.05 (95% CI -4.06; -2.04) IQ points per 1 mg/L up to 2 mg/L, becoming steeper above such level. A weaker and substantially linear decrease of -2.15 (95% CI -4.48; 0.18) IQ points with increasing urinary fluoride emerged above 0.28 mg/L (approximately reflecting a water fluoride content of 0.7 mg/L). The inverse association between fluoride exposure and IQ was particularly strong in the studies at high risk of bias, while no adverse effect emerged in the only study judged at low risk of bias. Overall, most studies suggested an adverse effect of fluoride exposure on children's IQ, starting at low levels of exposure. However, a major role of residual confounding could not be ruled out, thus indicating the need of additional prospective studies at low risk of bias to conclusively assess the relation between fluoride exposure and cognitive neurodevelopment.

Maternal Thyroid Dysfunction and Neuropsychological Development in Children

CONTEXT

Thyroid hormones are essential for fetal brain development. The potential effects of maternal gestational thyroid dysfunction on offspring neuropsychological development remain inconclusive.

OBJECTIVE

This work aimed to estimate effects of maternal thyroid dysfunction during pregnancy on offspring neuropsychological development in the first 2 years.

METHODS

We prospectively examined 1903 mothers and their children from the Shanghai Birth Cohort. Thyroid hormones were assessed at about 12 gestational weeks. Maternal thyroid function was classified into 7 categories: euthyroid, overt/subclinical hyperthyroidism, overt/subclinical hypothyroidism, hyperthyroxinemia, and hypothyroxinemia. Neuropsychological development was assessed by the Ages and Stages Questionnaire at age 6 months, and Bayley Scales at age 24 months.

RESULTS

Compared with children of euthyroid mothers, maternal overt hypothyroidism was associated with 7.0 points (95% CI, 1.7-12.4) lower scores in personal-social domain in girls aged 6 months, 7.3 points (95% CI, 2.0-12.6) lower in motor domain, and 7.7 points (95% CI, 1.1-14.2) lower social-emotional scores in boys at age 24 months; maternal subclinical hypothyroidism was associated with 6.5 points (95% CI, 1.0-12.1) poorer social-emotional domain in boys at age 6 months, and 7.4 points (95% CI, 0.1-14.8) poorer adaptive behavior domain in boys at age 24 months; maternal hypothyroxinemia was associated with 9.3 points (95% CI, 3.5-15.1) lower motor scores in boys at age 24 months; and maternal subclinical hyperthyroidism was associated with 6.9 points (95% CI, 0.1-13.7) lower language scores in girls at age 24 months.

CONCLUSION

Maternal overt hypothyroidism, subclinical hypothyroidism/hyperthyroidism, and hypothyroxinemia during early pregnancy were associated with weakened neuropsychological development in infancy, and some effects may be sex specific.

Evaluating the Progression to Hypothyroidism in Preconception Euthyroid Thyroid Peroxidase Antibody-Positive Women

CONTEXT

Thyroid peroxidase antibody (TPOAb) positivity is prevalent in women of reproductive age and predisposes to thyroid dysfunction, particularly hypothyroidism, which has adverse effects on pregnancy.

OBJECTIVE

This study aimed to report the rate of development of abnormal thyroid function among initially euthyroid TPOAb-positive women recruited into the TABLET trial, to identify factors associated with the development of hypothyroidism, and to compare outcomes between euthyroid and treated hypothyroid individuals.

METHODS

This observational cohort study, conducted at 49 UK hospitals between 2011 and 2016, included euthyroid TPOAb-positive women 16 to 40 years of age with a history of miscarriage or subfertility, planning pregnancy, randomized to levothyroxine 50 mcg daily or placebo. Abnormal thyroid function, conception rate, and live birth rate (LBR) ≥34 weeks were analyzed.

RESULTS

Among the women, 70/940 (7.4%) developed subclinical (SCH) or overt (OH) hypothyroidism: 27/470 taking levothyroxine and 43/470 placebo (relative risk [RR] 0.63; 95% CI, 0.39-1.00; P = 0.05); 83% of cases emerged prepregnancy. Baseline median serum TSH concentrations and TPOAb titers were significantly higher in those who developed hypothyroidism vs those who did not (P < 0.001). Treated SCH/OH demonstrated a higher failure-to-conceive rate compared with euthyroid women (adjusted RR 2.02 [1.56-2.62]; P < 0.001). The LBR ≥ 34 weeks was similar in the treated SCH/OH and euthyroid groups (adjusted RR 1.09 [0.77-1.55]; P = 0.6).

CONCLUSION

Approximately 7% of euthyroid TPOAb-positive women will develop hypothyroidism within 1 year preconception or in pregnancy. Conception rates are lower in women with treated SCH/OH compared with euthyroid women, but LBR are comparable. Thyroid function in TPOAb-positive women should be monitored regularly, when trying to conceive, to ensure prompt diagnosis and appropriate treatment initiation.

Endocrine disrupting chemicals: effects on pituitary, thyroid and adrenal glands

BACKGROUND

In recent years, scientific research has increasingly focused on Endocrine Disrupting Chemicals (EDCs) and demonstrated their relevant role in the functional impairment of endocrine glands. This induced regulatory authorities to ban some of these compounds and to carefully investigate others in order to prevent EDCs-related conditions. As a result, we witnessed a growing awareness and interest on this topic.

AIMS

This paper aims to summarize current evidence regarding the detrimental effects of EDCs on pivotal endocrine glands like pituitary, thyroid and adrenal ones. Particularly, we directed our attention on the known and the hypothesized mechanisms of endocrine dysfunction brought by EDCs. We also gave a glimpse on recent findings from pioneering studies that could in the future shed a light on the pathophysiology of well-known, but poorly understood, endocrine diseases like hormone-producing adenomas.

CONCLUSIONS

Although intriguing, studies on endocrine dysfunctions brought by EDCs are challenging, in particular when investigating long-term effects of EDCs on humans. However, undoubtedly, it represents a new intriguing field of science research.

Schmidt R, N. Pearce E. Prenatal Exposure to Per- and Polyfluoroalkyl Substances, Maternal Thyroid Dysfunction, and Child Autism Spectrum Disorder

Autism spectrum disorder (ASD), with its high economic and societal costs, is a growing public health concern whose prevalence has risen steadily over the last two decades. Although actual increased incidence versus improved diagnosis remains controversial, the increased prevalence of ASD suggests non-inherited factors as likely contributors. There is increasing epidemiologic evidence that abnormal maternal thyroid function during pregnancy is associated with increased risk of child ASD and other neurodevelopmental disorders. Prenatal exposure to endocrine-disrupting chemicals such as per- and polyfluoroalkyl substances (PFAS) is known to disrupt thyroid function and can affect early brain development; thus, thyroid dysfunction is hypothesized to mediate this relationship. The concept of a potential pathway from prenatal PFAS exposure through thyroid dysfunction to ASD etiology is not new; however, the extant literature on this topic is scant. The aim of this review is to evaluate and summarize reports with regard to potential mechanisms in this pathway.

Obstetric and offspring outcomes in isolated maternal hypothyroxinaemia: a systematic review and meta-analysis

OBJECTIVE

To examine the association between isolated maternal hypothyroxinaemia (IMH) and adverse obstetric outcomes and offspring outcomes and also investigate the effects of levothyroxine therapy on IMH for the above outcomes.

METHODS

We systematically searched PubMed, EMBASE, and Cochrane Library, and the reference lists of key reviews were hand searched on June 9, 2021. Two authors independently screened titles/abstracts. Full articles were further assessed if the information suggested that the study met the inclusion/exclusion criteria, and two researchers performed data extraction and risk-of-bias assessment using standardized tables. Summary relative risks or the mean difference between maternal effects and offspring outcomes were calculated by a random-effects model.

RESULTS

We identified 38 eligible articles (35 cohort studies and two randomized controlled trials [RCT]). Meta-analysis showed that maternal IMH was associated with increased gestational diabetes mellitus, preterm premature rupture of membranes, preterm birth, fetal distress, and macrosomia outcomes in IMH compared to euthyroid women, and the relative risks were 1.42 (1.03-1.96), 1.50 (1.05-2.14), 1.33 (1.15-1.55), 1.75 (1.16-2.65) and 1.62 (1.35-1.94), respectively. IMH was not associated with placenta previa, gestational hypertension, pre-eclampsia, intrauterine growth restriction, and offspring outcomes like birth weight, low birth weight infants, fetal macrosomia, neonatal intensive care, neonatal death, or fetal head circumference. In addition, we did not find an association between IMH and adverse offspring cognitive defects. Due to insufficient data for meta-analysis, it failed to pool the evidence of levothyroxine's therapeutic effect on IMH and their offspring.

CONCLUSIONS AND RELEVANCE

IMH in pregnancy may relate to a few maternal and offspring outcomes. Moreover, there is currently no sufficient evidence that levothyroxine treatment during pregnancy reduces adverse maternal outcomes and disability in offspring. Further investigation to explore the beneficial effects of levothyroxine therapy is warranted.

Under and overtreatment with thyroid hormone replacement during pregnancy

PURPOSE OF REVIEW

Among pregnant women on thyroid hormone replacement therapy undertreatment is common, while overtreatment is rare. Both deficient and excessive maternal thyroid hormone have been related to adverse maternofetal and long-term offspring outcomes, although studies' results are inconsistent. This review aims to discuss recent evidence regarding the effects of under- and overtreatment with thyroid hormone replacement during pregnancy and how current practices could be improved.

RECENT FINDINGS

Whether or not thyroid hormone therapy needs to be initiated for maternal subclinical hypothyroidism remains unclear, but recent meta-analyses have confirmed associations between adverse maternal, neonatal, and offspring outcomes in both overt and subclinical hypothyroidism. Subclinical hyperthyroidism in pregnancy is related to fewer adverse outcomes. Current adherence to levothyroxine during pregnancy and medication counseling by healthcare providers are suboptimal.

SUMMARY

Undertreatment of maternal hypothyroidism may increase risks for adverse maternofetal and offspring effects more than overtreatment does. If thyroid hormone replacement therapy is indicated and initiated in pregnancy, frequent thyroid function monitoring is required to avoid under- or overtreatment. Effective communication between clinicians and patients is imperative to increase medication adherence.

Late offspring effects of antenatal thyroid screening

BACKGROUND

Thyroid dysfunction in pregnancy is associated with adverse offspring outcomes and recent birth-cohort studies suggest that even mild degrees of thyroid dysfunction may be linked with a range of late cognitive and behavioural effects in childhood and adolescence.

SOURCES OF DATA

This review summarizes recent literature of observational studies and critically appraises randomized controlled trials (RCTs) of antenatal thyroid screening and Levothyroxine intervention.

AREAS OF AGREEMENT

Overt hypothyroidism and hyperthyroidism carry significant risks for unfavourable offspring outcomes and should be appropriately corrected in pregnancy.

AREAS OF CONTROVERSY

The significance of subclinical hypothyroidism and hypothyroxinaemia is still unclear. Meta-analyses of birth-cohort studies show associations of maternal subclinical hypothyroidism and hypothyroxinaemia with intellectual deficits, attention deficit hyperactivity disorder (ADHD) and autism spectrum disorders, while hyperthyroidism and high-normal FT4 were linked with ADHD. RCTs have shown no benefits of screening on neurodevelopmental outcomes although Levothyroxine could have been initiated too late in pregnancy in these trials.

GROWING POINTS

A small number of studies have shown inconsistent associations of maternal thyroid dysfunction with offspring cardiometabolic indices including blood pressure and body weight. Correction of maternal thyroid dysfunction was, however, associated with favourable long-term metabolic profiles in mothers, including lipid profiles, fat mass and body mass index. Antenatal thyroid screening may therefore present opportunities for optimizing a wider range of outcomes than envisaged.

AREAS FOR DEVELOPING RESEARCH

Future trials with early antenatal thyroid screening and intervention are necessary to clarify the impact of screening on late offspring and maternal effects.

Domain-specific effects of prenatal fluoride exposure on child IQ at 4, 5, and 6-12 years in the ELEMENT cohort

OBJECTIVE

Prenatal exposure to fluoride has been associated with adverse neurodevelopmental outcomes. However, the neuropsychological profile of fluoride's developmental neurotoxicity at low levels and the stability of this relationship across childhood has not been characterized. We investigated the longitudinal and domain specific effect of prenatal fluoride exposure on IQ among children ages 4, 5, and 6-12 years in the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) cohort.

METHODS

We measured the average of maternal urinary fluoride at each trimester of pregnancy adjusted for creatinine (MUF_CRE). Children were administered the McCarthy Scales of Children's Abilities at ages 4 (N = 386) and 5 (N = 308), and the Wechsler Abbreviated Scale of Intelligence at age 6-12 (N = 278). We used generalized estimating equation (GEE) models to estimate the population averaged effect of MUF_CRE concentration on longitudinal General Cognitive Index (GCI)/Full-Scale IQ (FSIQ), Verbal IQ (VIQ), and Performance IQ (PIQ) scores (N = 348). We tested for possible interactions between MUF_CRE and child sex as well as for MUF_CRE and time point on children's IQ. All models controlled for relevant available covariates.

RESULTS

The mean/median MUF_CRE concentration was 0.90/0.83 mg/L (SD = 0.39; IQR, 0.64-1.11 mg/L). A 0.5 mg/L increase in MUF_CRE predicted an average 2.12-point decrease in GCI/FSIQ (95% CI: -3.49, -0.75) and 2.63-point decrease in PIQ (95% CI: -3.87, -1.40). MUF_CRE was marginally associated with VIQ across time (B = -1.29, 95% CI: -2.60, 0.01). No interactions between MUF_CRE and child sex or MUF_CRE and time were observed.

CONCLUSION

The negative association between prenatal fluoride exposure and longitudinal IQ was driven by decrements in non-verbal intelligence (i.e. PIQ), suggesting that visual-spatial and perceptual reasoning abilities may be more impacted by prenatal fluoride exposure as compared to verbal abilities.

Selenium Status and Supplementation Effects in Pregnancy—A Study on Mother–Child Pairs from a Single-Center Cohort

The demand for selenium (Se) increases during pregnancy since this element supports child growth, proper neuronal development and maternal thyroid function. The issue is particularly relevant for populations living in areas with a limited selenium supply, where many pregnant women opt for Se supplementation. The efficiency of this measure is unknown, although it seems vital in the prevention of severe Se deficiency. In order to evaluate this hypothesis, an observational study was conducted in Poland, where Se deficiency is prevalent. Pregnant women were invited to participate in the study and provided serum samples at the end of pregnancy (n = 115). Information on the supplemental intake of micronutrients was recorded in a face-to-face interview. In addition, serum samples were isolated from the cord blood of newborns at delivery (n = 112) and included in the analyses. Thyroid hormone status was evaluated by routine laboratory tests, and Se status was determined by total Se and selenoprotein P (SELENOP) concentrations and extracellular glutathione peroxidase (GPX3) activity. The three parameters of Se status correlated strongly within the group of mothers and within the group of newborns, with an additional significant correlation found among mother–child pairs. One-third of mothers reported additional Se intake, mainly as a component of multi-micronutrient supplements, at a mean (±SD) dosage of 42 ± 14 µg Se/day. Despite this regime, most of the women presented an insufficient Se status, with 79% of mothers displaying serum Se concentrations below 70 µg/L (indicating Se deficiency) and 22% showing levels below 45.9 µg/L (severe Se deficiency). The inadequate Se supply was also reflected in relatively low SELENOP concentrations and GPX3 activity. Neither total Se nor SELENOP or GPX3 levels were significantly higher in the group of mothers reporting the intake of supplements than in the non-supplementing group. Nevertheless, elevated SELENOP concentrations were observed in the subgroup receiving supplements with more than 55 µg/day. We conclude that the self-administered supplementation of small Se dosages was not sufficient to achieve replete Se status in the micronutrient scant area. However, the maternal Se deficit measured by either Se, SELENOP or GPX3 was transferred from mothers to the newborns, as the parameters correlated strongly in the mother–newborn pairs of samples. It is vital to re-evaluate the guidelines concerning pregnancy care and monitoring of micronutrient status during pregnancy, in particular in areas where deficiencies are present.

Association between Hypertensive Disorders of Pregnancy and Long-Term Neurodevelopmental Outcomes in the Offspring

OBJECTIVE

The long-term impact of hypertensive disorders of pregnancy (HDP) exposure on offspring health is an emerging research area. The objective of this study was to evaluate the association between a maternal diagnosis of HDP (gestational hypertension and preeclampsia) and adverse neurodevelopmental outcomes in the offspring.

STUDY DESIGN

This was a secondary analysis of two parallel multicenter clinical trials of thyroxine therapy for subclinical hypothyroid disorders in pregnancy. Women with singleton nonanomalous gestations diagnosed with subclinical hypothyroidism or hypothyroxinemia were randomized to thyroxine therapy or placebo. The primary outcome was child intelligence quotient (IQ) at 5 years of age. Secondary outcomes included several neurodevelopmental measures, including the Bayley-III cognitive, motor, and language scores at 12 and 24 months, Differential Ability Scales-II (DAS-II) scores at 36 months, the Conners' rating scales-revised at 48 months, and scores from the Child Behavior Checklist at 36 and 60 months. Thyroxine therapy did not influence neurodevelopment in either of the primary studies. Associations between neurodevelopment outcomes and maternal HDP were examined using univariable and multivariable analyses.

RESULTS

A total of 112 woman-child dyads with HDP were compared with 1,067 woman-child dyads without HDP. In univariable analysis, mean maternal age (26.7 ± 5.9 vs. 27.8 ± 5.7 years, p = 0.032) and the frequency of nulliparity (45.5 vs. 31.0%, p = 0.002) differed significantly between the two groups. Maternal socioeconomic characteristics did not differ between the groups. After adjusting for potential confounders, there were no significant differences in any primary or secondary neurodevelopment outcome between offspring exposed to HDP and those unexposed. However, when dichotomized as low or high scores, we found higher rates of language delay (language scores <85: -1 standard deviation) at 2 years of age among offspring exposed to HDP compared with those unexposed (46.5 vs. 30.5%, adjusted odds ratio = 2.22, 95% confidence interval [CI]: 1.44-3.42).

CONCLUSION

In this cohort of pregnant women, HDP diagnosis was associated with language delay at 2 years of age. However, other long-term neurodevelopmental outcomes in offspring were not associated with HDP.

KEY POINTS

· No differences were found in neurodevelopment between offspring exposed to HDP and controls.. · Higher rates of language delay at 2 years of age were found in offspring exposed to HDP.. · The results did not differ when analysis was stratified by preterm birth..

Hypothyroidism

Hypothyroidism is the common clinical condition of thyroid hormone deficiency and, if left untreated, can lead to serious adverse health effects on multiple organ systems, with the cardiovascular system as the most robustly studied target. Overt primary hypothyroidism is defined as elevated thyroid-stimulating hormone (TSH) concentration in combination with free thyroxine (fT₄) concentration below the reference range. Subclinical hypothyroidism, commonly considered an early sign of thyroid failure, is defined by elevated TSH concentrations but fT₄ concentrations within the reference range. Hypothyroidism is classified as primary, central or peripheral based on pathology in the thyroid, the pituitary or hypothalamus, or peripheral tissue, respectively. Acquired primary hypothyroidism is the most prevalent form and can be caused by severe iodine deficiency but is more frequently caused by chronic autoimmune thyroiditis in iodine-replete areas. The onset of hypothyroidism is insidious in most cases and symptoms may present relatively late in the disease process. There is a large variation in clinical presentation and the presence of hypothyroid symptoms, especially in pregnancy and in children. Levothyroxine (LT4) is the mainstay of treatment and is one of the most commonly prescribed drugs worldwide. After normalization of TSH and fT₄ concentrations, a considerable proportion of patients treated with LT4 continue to have persistent complaints, compromising quality of life. Further research is needed regarding the appropriateness of currently applied reference ranges and treatment thresholds, particularly in pregnancy, and the potential benefit of LT4/liothyronine combination therapy for thyroid-related symptom relief, patient satisfaction and long-term adverse effects.

Management of Hypothyroidism and Hypothyroxinemia in Pregnancy

OBJECTIVE

To review the diagnosis and management of hypothyroidism in pregnancy, preconception, and the postpartum period.

METHODS

Literature review of English-language papers published between 1982 and 2022, focusing on the most recent literature.

RESULTS

During pregnancy, thyroid function laboratory tests need to be interpreted with regard to gestational age. Overt hypothyroidism, regardless of the TSH level, should always be promptly treated when it is diagnosed preconception or during pregnancy or lactation. Most women with preexisting treated hypothyroidism will require an increase in levothyroxine dosing to maintain euthyroidism during gestation. levothyroxine-treated pregnant patients need close monitoring with serum thyroid stimulating hormone (TSH) to avoid or- or under treatment. There is no consensus about whether to initiate levothyroxine in women with mild forms of gestational thyroid hypofunction. However, in light of current evidence it is reasonable to treat subclinically hypothyroid women with levothyroxine, particularly if the TSH is >10 mIU/L or the thyroperoxidase antibody is positive. Women who are not treated need to be followed to ensure that treatment is initiated promptly if thyroid failure progresses. Additional studies are needed to better understand the effects of the initiation of levothyroxine in early gestation in subclinically hypothyroid and hypothyroxinemic women and to determine optimal strategies for thyroid function screening in preconception and pregnancy.

CONCLUSION

The diagnosis and management of hypothyroidism in the peripregnancy period present specific challenges. In making management decisions, it is essential to weigh the risks and benefits of treatments not just for the mother but also for the fetus.

The Role of Iodine for Thyroid Function in Lactating Women and Infants

Iodine is a micronutrient needed for the production of thyroid hormones, which regulate metabolism, growth, and development. Iodine deficiency or excess may alter the thyroid hormone synthesis. The potential effects on infant development depend on the degree, timing, and duration of exposure. The iodine requirement is particularly high during infancy because of elevated thyroid hormone turnover. Breastfed infants rely on iodine provided by human milk, but the iodine concentration in breast milk is determined by the maternal iodine intake. Diets in many countries cannot provide sufficient iodine, and deficiency is prevented by iodine fortification of salt. However, the coverage of iodized salt varies between countries. Epidemiological data suggest large differences in the iodine intake in lactating women, infants, and toddlers worldwide, ranging from deficient to excessive intake. In this review, we provide an overview of the current knowledge and recent advances in the understanding of iodine nutrition and its association with thyroid function in lactating women, infants, and toddlers. We discuss risk factors for iodine malnutrition and the impact of targeted intervention strategies on these vulnerable population groups. We highlight the importance of appropriate definitions of optimal iodine nutrition and the need for more data assessing the risk of mild iodine deficiency for thyroid disorders during the first 2 years in life.

TPO antibody in euthyroid pregnant women and cognitive ability in the offspring: a focused review

PURPOSE

A link between maternal thyroid dysfunction during pregnancy and the risk of cognitive and behavioral problems in the offspring has previously been established; however, the potential effects of maternal thyroid autoimmunity on neurodevelopment in the absence of maternal hypothyroidism are less clear. The present review aims to highlight the gaps in knowledge in this regard and provide a thorough assessment of relevant literature.

METHOD

Related keywords searched in MEDLINE, Web of Science, and Scopus till January 2021.

RESULTS

There is some evidence that neuropsychological and intellectual developments of offspring are adversely affected by maternal thyroid autoimmunity, although the results of available studies are not concordant. The tools and measurements that have been applied in different studies to assess neurodevelopment or IQ vary widely and the children born to mothers with thyroid autoimmunity have been assessed at different chronological stages of life. Such variations may explain some of the differences across studies. In addition, the definition of thyroid autoimmunity has been based on TPOAb cut points provided by manufacturers in most cases, but it is preferable to define these values based on age, trimester, and method-specific reference ranges.

CONCLUSION

Well-designed studies are needed to assess verbal and non-verbal neurocognition of offspring born to mothers with autoimmune thyroid disease before or during pregnancy.

Effect of Levothyroxine on Pregnancy Outcomes in Pregnant Women With Hypothyroxinemia: An Interventional Study

CONTEXT

Adverse maternal outcomes and perinatal complications are associated with maternal hypothyroidism. However, the utility of levothyroxine (L-T4) in the treatment of pregnant women with hypothyroxinemia is unclear.

OBJECTIVE

This study aimed to evaluate the effects of L-T4 on maternal and perinatal outcomes in pregnant women with hypothyroxinemia.

METHODS

The nonrandomized interventional study was conducted at Shanghai First Maternity and Infant Hospital, Punan Hospital of Shanghai, and Beicai Community Health Center of Shanghai. The pregnant women with hypothyroxinemia from the first trimester were enrolled and divided into treatment and control groups. 463 taking L-T4 and 501 not administering L-T4 were analyzed in the study. All participants were screened for TPOAB/TGAB antibody status.

MAIN OUTCOME

The primary outcome of the study was the hypertensive disorder of pregnancy (HDP), measured as the proportion of HDP. In addition to this primary outcome, some secondary outcomes will be measured: miscarriage, gestational diabetes mellitus, premature rupture of membranes, placental abruption, intrahepatic cholestasis of pregnancy, fetal distress, macrosomia, and neonates admitted to the neonatal intensive care unit (NICU). The effects of L-T4 on the incidence of adverse pregnancy outcomes and perinatal complications were compared.

RESULTS

Multivariate logistic regression analysis showed that L-T4 treatment (adjusted odds ratio = 1.78 [95% CI = 1.00-3.16], p = 0.04) significantly reduced the incidence of miscarriage. Otherwise, lower neonates admitted to the NICU were strongly associated with the L-T4 group (adjusted odds ratio = 1.36 [95% CI = 1.01 - 1.83], p = 0.04). There were no significant differences in the incidence rates of other adverse maternal outcomes and perinatal complications between pregnant women with hypothyroxinemia receiving and those not receiving L-T4 treatment.

CONCLUSION

The incidence of HDP was not significantly reduced using L-T4 in pregnant women with hypothyroxinemia. The results of this study also showed that L-T4 treatment significantly reduced the miscarriages rate and the proportion of newborns admitted to the NICU.

The Impact of Bisphenol A on Thyroid Function in Neonates and Children: A Systematic Review of the Literature

Background: Bisphenol A (BPA) is an endocrine-disrupting chemical widely used in plastic products that may have an adverse effect on several physiologic functions in children. The aim of this systematic review is to summarize the current knowledge of the impact of BPA concentrations on thyroid function in neonates, children, and adolescents. Methods: A systematic search of Medline, Scopus, Clinical Trials.gov, Cochrane Central Register of Controlled Trials CENTRAL, and Google Scholar databases according to PRISMA guidelines was performed. Only case–control, cross-sectional, and cohort studies that assessed the relationship between Bisphenol A and thyroid function in neonates and children aged <18 years were included. Initially, 102 articles were assessed, which were restricted to 73 articles after exclusion of duplicates. A total of 73 articles were assessed by two independent researchers based on the title/abstract and the predetermined inclusion and exclusion criteria. According to the eligibility criteria, 18 full-text articles were selected for further assessment. Finally, 12 full-text articles were included in the present systematic review. Results: The presented studies offer data that suggest a negative correlation of BPA concentrations with TSH in children, a gender-specific manner of action, and a potential effect on proper neurodevelopment. However, the results are inconclusive with respect to specific thyroid hormone concentrations and the effect on thyroid autoimmunity. Conclusion: The potential negative effect of BPA in the developing thyroid gland of children that may affect proper neurodevelopment, suggesting the need to focus future research on designing studies that elucidate the underlying mechanisms and the effects of BPA in thyroid function in early life.

Early postnatal hypothyroidism reduces juvenile play behavior, but prenatal hypothyroidism compensates for these effects

Perinatal hypothyroidism causes long-lasting effects on behavior, including hyperactivity, cognitive delays/deficits, and a reduction in anxiety. Although there is some evidence that hypothyroidism during fetal development in humans has been associated with later autism spectrum disorder diagnosis or autism-like traits, the relationships between early thyroid hormones and social behaviors are largely unknown. Previously, we found that a moderate dose of the hypothyroid-inducing drug methimazole during embryonic and postnatal development dramatically increased juvenile play in male and female rats. The goal of the current study was to determine the extent to which thyroid hormones act in prenatal or postnatal development to organize later social behaviors. Subjects were exposed to methimazole in the drinking water during prenatal (embryonic day 12 to birth), postnatal (birth to postnatal day 23), or pre- and postnatal development; control animals received regular drinking water throughout the experiment. They were tested for play behavior as juveniles (P30-32). We found an interaction between pre- and postnatal methimazole administration such that postnatal hypothyroidism decreased some play behaviors, whereas sustained pre- and postnatal hypothyroidism restored play to control levels. The effects were similar in males and females. To our knowledge, this is the first report of an interaction between pre- and postnatal hypothyroidism on later behavior. The complexity of the timing of these effects may help explain why epidemiological studies have not consistently found a relationship between gestational hypothyroidism and later behavior.

Preconceptional and the first trimester exposure to PM2.5 and offspring neurodevelopment at 24 months of age: Examining mediation by maternal thyroid hormones in a birth cohort study

Prenatal fine particulate matter (PM_2.5) exposure has been associated with impaired offspring neurodevelopment; however, the association of PM_2.5 exposure during preconception with offspring's neurodevelopment and factors responsible for this association are still unclear. This study estimated the associations of PM_2.5 exposure during preconception and the first trimester with offspring neurodevelopment and evaluated whether maternal thyroid hormones mediate these associations. We recruited 1329 mother-child pairs between 2013 and 2015 in Wuhan, China. PM_2.5 exposure levels of each woman during the 3 months preconception and the first trimester were estimated using land-use regression models. Offspring neurodevelopment characterized by mental developmental index (MDI) and psychomotor developmental index (PDI) were measured at 24 months of age. Maternal serum levels of free thyroxine (FT3), free triiodothyronine (FT4), and thyroid-stimulating hormone (TSH) during early pregnancy were measured of a subset of the 1329 women (551 women). Generalized estimation equation and general linear regression models were used to estimate the associations between maternal PM_2.5 exposure, thyroid hormones, and offspring neurodevelopment. After adjusting for potential confounders, we found that either among all participants or the subset, PM_2.5 exposure during preconception and the first trimester was negatively associated with offspring PDI. Double increment in the first trimester PM_2.5 exposure was significantly associated with 3.43 and 6.48 points decrease in offspring MDI. In the subset, each doubling of PM_2.5 exposure during preconception and the first trimester was significantly associated with 7.93 and 8.02 points decrease in maternal FT4 level, respectively. Increased maternal FT4, in turn, was associated with increased PDI (β = 16.69, 95% CI: 5.39, 27.99). About 7.7% (95% CI: 2.0%-19.4%) and 8.6% (95% CI: 3.0%, 22.1%) of the effect of PM_2.5 exposure during preconception on offspring PDI was mediated through maternal FT4 and the FT4/FT3 ratio, respectively.

Free thyroxine in early pregnancy is an independent negative predictor of 3rd trimester HbA1c. Odense child cohort

BACKGROUND

Lower thyroid function outside pregnancy is associated with an increased risk of type 2 diabetes mellitus. The relationship between thyroid function in early pregnancy and glucose status in 3rd trimester has not been investigated.

AIMS

To study the association between 1st trimester thyroid function and 3rd trimester glucose status.

DESIGN

In the prospective study Odense Child Cohort (OCC), 1,041 women had 1st trimester blood samples analysed for thyroid-stimulating hormone (TSH), free T4 (FT4), thyroid peroxidase antibody and HbA1c. Third trimester (week 28) fasting blood samples included plasma glucose, insulin and HbA1c. Oral glucose tolerance test (OGTT, 75 g glucose) was performed in 509 women. First trimester FT4 was dichotomized >vs. ≤ the 25th percentile (25p = 12.9 pmol/L). Homeostatic model assessment-insulin resistance (HOMA)-IR and HOMA-β were calculated.

RESULTS

Women with FT4 ≤25p had significantly higher HbA1c in 1st and 3rd trimesters and higher 3rd trimester fasting glucose, insulin, HOMA-IR and HOMA-β compared to women with FT4 >25p. In multiple regression analyses, FT4 was an independent negative predictor of 3rd trimester HbA1c. FT4 levels in 3rd and 4th quartiles (high-normal FT4 levels) showed closest inverse associations with HbA1c (p-trend <.001). TSH was not associated with 3rd trimester HbA1c.

CONCLUSION

Women with lower levels of FT4 in early pregnancy had higher HbA1c in 3rd trimester and FT4 was an independent negative predictor of 3rd trimester HbA1c.

Perinatal exposure to endocrine disrupting chemicals and neurodevelopment: How articles of daily use influence the development of our children

Substances that interfere with the body's hormonal balance or their function are called endocrine disrupting chemicals (EDCs). Many EDCs are ubiquitous in the environment and are an unavoidable aspect of daily life, including during early embryogenesis. Developmental exposure to these chemicals is of critical relevance, as EDCs can permanently alter developmental programs, including those that pattern and wire the brain. Of emerging interest is how these chemicals may also affect the immune response, given the cross-talk between the endocrine and immune systems. As brain development is strongly dependent on hormones including thyroid, androgens, and estrogens, and can also be affected by immunomodulation, this complicated interplay may have long-lasting neurodevelopmental consequences. This review focuses on data available from human cohorts, in vivo models, and in vitro assays regarding the impact of EDCs after a gestational and/or lactational exposure, and how they may impact the immune system and/or neurodevelopment.

Neurodevelopmental impact of the offspring by thyroid hormone system-disrupting environmental chemicals during pregnancy

Everyday use chemicals have been demonstrated to be endocrine disruptors. Since normal thyroid function during pregnancy is transcendental for the neurodevelopment of the offspring, knowledge of endocrine disrupting chemicals (EDC) is of main importance. The aim of our study is to recognize and describe EDC actions in pregnant women and focus on neurodevelopmental processes that can lead to neurotransmitter imbalance and cognitive impairment, and the possible clinical outcomes in the newborn and child. We searched PubMed databases for animal studies and clinical trials evaluating chemicals recognized as thyroid disruptors -perchlorate, phthalates, bisphenol A-, as well as chemicals with potential thyroid disruption activity -parabens, pesticides and persistent organic pollutants, on thyroid hormones (THs) levels and their bioavailability during pregnancy, and the outcome in newborns, infants and children. We also exhibit evidence from worldwide cohort studies to this regard. The publications reviewed show: 1) known endocrine disruptors have an association with hormonal thyroid levels, where an effect of increase or decrease in TH concentrations has been reported depending on the chemical exposed 2) associations between TH, EDCs and neurocognitive disorders have been addressed, such as ADHD, though no conclusive impact on potential related disorders as autism has been established, 3) perchlorate has demonstrated effects on thyroid levels on iodine uptake. In conclusion, detrimental risks and long-term consequences after in-utero exposure to EDCs are being reported in several cohort studies and further research must be conducted to establish a well-known cause-effect association.

Associations between maternal thyroid function in pregnancy and child neurodevelopmental outcomes at 20 months in the Seychelles Child Development Study, Nutrition Cohort 2 (SCDS NC2)

Maternal thyroid hormones facilitate optimal foetal neurodevelopment; however, the exact role of the thyroid hormones on specific cognitive outcomes is unknown. The present study aimed to investigate associations between maternal thyroid function and neurodevelopmental outcomes in the Seychelles Child Development Study (SCDS) Nutrition 2 cohort (n 1328). Maternal free thyroid hormones (fT3, fT4 and fTSH) were assessed at 28 weeks' gestation with a range of child cognitive outcomes analysed at 20 months. Dietary iodine intake was analysed for a subset of women through a Food Frequency Questionnaire. Linear regression analysis was used to test associations between serum concentrations of maternal thyroid hormones and child neurodevelopment outcomes. Thyroid hormones were analysed as continuous data and categorised as quintiles. 95% of mothers had optimal thyroid function based on fTSH concentrations. Overall, the present study shows that maternal thyroid function is not associated with neurodevelopmental outcomes in this high fish-eating population. However, a positive association, using quintiles for fT3, was reported for the Mental Developmental Index, between Q3 v. Q4 (β 0⋅073; P 0⋅043) and for Q3 v. Q5 (β value 0⋅086; P 0⋅018). To conclude, mothers in our cohort, who largely have optimal thyroid function and iodine intakes, appear able to regulate thyroid function throughout pregnancy to meet neurodevelopmental needs. However, it is possible that minor imbalances of fT3, as indicated from our secondary analysis, may impact offspring neurodevelopment. Further investigation of the relationship between maternal thyroid function and infant neurodevelopment is warranted, particularly in populations with different dietary patterns and thereby iodine intakes.

Influence of the Aryl Hydrocarbon Receptor Activating Environmental Pollutants on Autism Spectrum Disorder

Autism spectrum disorder (ASD) is an umbrella term that includes many different disorders that affect the development, communication, and behavior of an individual. Prevalence of ASD has risen exponentially in the past couple of decades. ASD has a complex etiology and traditionally recognized risk factors only account for a small percentage of incidence of the disorder. Recent studies have examined factors beyond the conventional risk factors (e.g., environmental pollution). There has been an increase in air pollution since the beginning of industrialization. Most environmental pollutants cause toxicities through activation of several cellular receptors, such as the aryl hydrocarbon receptor (AhR)/cytochrome P450 (CYPs) pathway. There is little research on the involvement of AhR in contributing to ASD. Although a few reviews have discussed and addressed the link between increased prevalence of ASD and exposure to environmental pollutants, the mechanism governing this effect, specifically the role of AhR in ASD development and the molecular mechanisms involved, have not been discussed or reviewed before. This article reviews the state of knowledge regarding the impact of the AhR/CYP pathway modulation upon exposure to environmental pollutants on ASD risk, incidence, and development. It also explores the molecular mechanisms involved, such as epigenesis and polymorphism. In addition, the review explores possible new AhR-mediated mechanisms of several drugs used for treatment of ASD, such as sulforaphane, resveratrol, haloperidol, and metformin.

Iodine Nutrition and Iodine Supplement Initiation in Association with Thyroid Function in Mildly-to-Moderately Iodine-Deficient Pregnant and Postpartum Women

BACKGROUND

Whereas the adverse effects of severe iodine deficiency during pregnancy are well documented, the effects of mild-to-moderate deficiency are not well established.

OBJECTIVES

We aimed to explore whether iodine nutrition and timing of iodine supplement initiation are associated with thyroid function in pregnant and postpartum women.

METHODS

In this cohort study, 137 pregnant women were enrolled and followed up at gestational weeks (GWs) 18 and 36, and 3 and 6 mo postpartum. Thyroid function tests [thyroid-stimulating hormone (TSH), free triiodothyronine (fT3), and free thyroxine (fT4)], urinary iodine and creatinine concentration (UIC:Cr), and iodine intake (including iodine supplement use) were measured at each time point. The associations between thyroid hormone concentrations and UIC:Cr, iodine intakes, and iodine supplement use were estimated using multiple generalized estimating equation models.

RESULTS

The median UIC at GW18 was 94 μg/L, indicating mild-to-moderate iodine deficiency. UIC:Cr (β; 95% CI) per 100 μg/g was negatively associated with fT3 (-0.191; -0.331, -0.051) and fT4 (-0.756; -1.372, -0.141) concentrations. Iodine intake (β; 95% CI) per 100 μg/d was positively associated with TSH (0.099; 0.022, 0.177), and negatively associated with fT3 (-0.084; -0.0141, -0.027) and fT4 (-0.390; -0.599, -0.182) concentrations. Compared with no use of supplement, those initiating an iodine-containing supplement prepregnancy and continuing through pregnancy had lower TSH (estimated means) (1.35 compared with 1.68 mIU/L, P = 0.021), and higher fT3 (4.48 compared with 4.28 pmol/L, P = 0.035) and fT4 (15.2 compared with 14.4 pmol/L, P = 0.024) concentrations.

CONCLUSIONS

Lower iodine availability during pregnancy and postpartum was associated with lower TSH, and higher fT3 and fT4 concentrations. The use of an iodine-containing supplement that was initiated prepregnancy and continuing through pregnancy was associated with lower TSH, and higher fT3 and fT4 concentrations, which may suggest improved thyroid function. These findings support the notion that optimization of iodine intake should start before pregnancy.This trial was registered at clinicaltrials.gov as NCT02610959.

Evidence-Based Recommendations for an Optimal Prenatal Supplement for Women in the U.S., Part Two: Minerals

The levels of many essential minerals decrease during pregnancy if un-supplemented, including calcium, iron, magnesium, selenium, zinc, and possibly chromium and iodine. Sub-optimal intake of minerals from preconception through pregnancy increases the risk of many pregnancy complications and infant health problems. In the U.S., dietary intake of minerals is often below the Recommended Dietary Allowance (RDA), especially for iodine and magnesium, and 28% of women develop iron deficiency anemia during their third trimester. The goal of this paper is to propose evidence-based recommendations for the optimal level of prenatal supplementation for each mineral for most women in the United States. Overall, the evidence suggests that optimal mineral supplementation can significantly reduce a wide range of pregnancy complications (including anemia, gestational hypertension, gestational diabetes, hyperthyroidism, miscarriage, and pre-eclampsia) and infant health problems (including anemia, asthma/wheeze, autism, cerebral palsy, hypothyroidism, intellectual disability, low birth weight, neural tube defects, preterm birth, rickets, and wheeze). An evaluation of 180 commercial prenatal supplements found that they varied widely in mineral content, often contained only a subset of essential minerals, and the levels were often below our recommendations. Therefore, there is a need to establish recommendations on the optimal level of mineral supplementation during pregnancy.

Associations of Hypothyroxinemia With Risk of Preeclampsia-Eclampsia and Gestational Hypertension

OBJECTIVE

To investigate the association between hypothyroxinemia and the risk of preeclampsia-eclampsia and gestational hypertension.

DESIGN

Historical cohort study.

METHODS

The study included pregnant individuals who delivered live-born singletons and had at least one thyroid function assessment during pregnancy at a tertiary hospital. Hypothyroxinemia was defined as thyroid-stimulating hormone (TSH) levels within the normal reference range and free thyroxine (FT4) levels lower than the tenth percentile. Risk ratios (RRs) with 95% confidence intervals (95% CIs) for preeclampsia-eclampsia and gestational hypertension between women with and without a diagnosis of hypothyroxinemia during pregnancy were estimated using a generalized estimating equation model.

RESULTS

A total of 59,463 women with live-born singletons were included in the analysis. Logistic regression models with restricted cubic spline suggested that there was a U-shaped association between FT4 levels and preeclampsia-eclampsia risk. Compared with euthyroid women, those with hypothyroxinemia had an increased risk of preeclampsia-eclampsia (RR = 1.16, 95% CI: 1.02-1.31), and the risk increased with the increasing severity of hypothyroxinemia (p for trend < 0.001). Moreover, persistent hypothyroxinemia from the first to second trimesters was associated with an increased risk of preeclampsia-eclampsia (RR = 1.37, 95% CI: 1.03-1.83), especially for women with severe hypothyroxinemia (RR = 1.70, 95% CI: 1.12-2.58). In contrast, there was no association between hypothyroxinemia and gestational hypertension.

CONCLUSION

Our study suggested that hypothyroxinemia was only associated with an increased risk of preeclampsia-eclampsia, especially in women with persistent hypothyroxinemia in the first half of pregnancy. Analyses of the associated risk of gestational hypertension with hypothyroxinemia were not significant.

Toward a science-based testing strategy to identify maternal thyroid hormone imbalance and neurodevelopmental effects in the progeny - part I: which parameters from human studies are most relevant for toxicological assessments?

The 2018 European Food Safety Authority/European Chemicals Agency Guidance on the Identification of Endocrine Disruptors lacks clarity on how the presence or absence of substance-induced maternal thyroid hormone imbalance, or the potential for subsequent deleterious consequences in child neurodevelopment, should be established by toxicological assessments. To address these uncertainties, this narrative review evaluates human evidence on how altered maternal thyroid function may be associated with child neurodevelopmental outcomes; and seeks to identify parameters in human studies that appear most relevant for toxicological assessments. Serum levels of free thyroxine (fT4) and thyroid stimulating hormone (TSH) are most frequently measured when assessing thyroid function in pregnant women, whereas a broad spectrum of neurodevelopmental parameters is used to evaluate child neurodevelopment. The human data confirms an association between altered maternal serum fT4 and/or TSH and increased risk for child neurodevelopmental impairment. Quantitative boundaries of effects indicative of increased risks need to be established. Moreover, it is unknown if altered serum levels of total T4, free or total triiodothyronine, or parameters unrelated to serum thyroid hormones might be more relevant indicators of such effects. None of the human studies established a link between substance-mediated liver enzyme induction and increased serum thyroid hormone clearance, let alone further to child neurodevelopmental impairment. This review identifies research needs to contribute to the development of toxicity testing strategies, to reliably predict whether substances have the potential to impair child neurodevelopment via maternal thyroid hormone imbalance.

Thyroid disrupting chemicals and developmental neurotoxicity - New tools and approaches to evaluate hormone action

It is well documented that thyroid hormone (TH) action is critical for normal brain development and is mediated by both nuclear and extranuclear pathways. Given this dependence, the impact of environmental endocrine disrupting chemicals that interfere with thyroid signaling is a major concern with direct implications for children's health. However, identifying thyroid disrupting chemicals in vivo is primarily reliant on serum thyroxine (T4) measurements within greater developmental and reproductive toxicity assessments. These studies do not examine known TH-dependent phenotypes in parallel, which complicates chemical evaluation. Additionally, there exist no recommendations regarding what degree of serum T4 dysfunction is adverse, and little consideration is given to quantifying TH action within the developing brain. This review summarizes current testing strategies in rodent models and discusses new approaches for evaluating the developmental neurotoxicity of thyroid disrupting chemicals. This includes assays to identify adverse cellular effects of the brain by both immunohistochemistry and gene expression, which would compliment serum T4 measures. While additional experiments are needed to test the full utility of these approaches, incorporation of these cellular and molecular assays could enhance chemical evaluation in the regulatory arena.

Maternal and childhood urinary phenol concentrations, neonatal thyroid function, and behavioral problems at 10 years of age: The SMBCS study

BACKGROUND

Environmental phenols, bisphenol A (BPA), triclosan (TCS), and benzophenone-3 (BP-3), are known as emerging endocrine-disrupting chemicals; however, their impacts on thyroid hormones and children's neurobehaviors are still unclear.

OBJECTIVES

We aimed to examine the associations of prenatal and childhood exposure to phenols with neonatal thyroid function and childhood behavioral problems aged 10 years.

METHODS

A total of 386 mother-singleton pairs were included from Sheyang Mini Birth Cohort Study (SMBCS), a longitudinal birth cohort in China. We quantified urinary BPA, TCS and BP-3 concentrations in maternal and 10-year-old children's urine samples using gas chromatography tandem mass spectrometry and thyroid function parameters in cord serum samples. Caregivers completed the Strength and Difficulties Questionnaire (SDQ) for their children at 10 years of age. Multivariable linear regression models and logistic regression models were applied to estimate associations of urinary phenol concentrations with thyroid hormones and risks of children's behavioral problems, respectively.

RESULTS

The median values of urinary BPA, TCS and BP-3 concentrations for pregnant women were 1.75 μg/L, 0.54 μg/L and 0.37 μg/L, while 1.29 μg/L, 6.64 μg/L and 1.39 μg/L for children, respectively. Maternal urinary BPA concentrations were in associations with 1.00% [95% confidence interval (CI): 0.20%, 1.92%] increases in cord serum FT4 concentrations and significantly associated with increased risks of total difficulties [odds ratio (OR): 1.45, 95% CI: 1.07, 1.97], while maternal urinary levels of BP-3 were significantly related to poorer prosocial behaviors (OR: 1.58, 95% CI: 1.04, 2.39) of children at 10 years of age. In sex-stratified analyses, maternal urinary BPA concentrations were related to increased total difficulty subscales only in boys.

CONCLUSIONS

The findings indicated that higher prenatal urinary BPA concentrations were associated with increased risks of total difficulties, especially in boys and maternal urinary BP-3 concentrations were related to poorer prosocial behaviors at 10 years.

The Effect of Iodine-Containing Vitamin Supplementation During Pregnancy on Thyroid Function in Late Pregnancy and Postpartum Depression in an Iodine-Sufficient Area

The purpose of this study was to investigate the effect of iodine supplementation during pregnancy on thyroid function and also its effect on postpartum depression in an iodine-sufficient area. Healthy pregnant women were divided into three groups: group A (vitamin iodine-150) receiving vitamin containing 150 μg iodine, group B (vitamin iodine-0) receiving vitamin without iodine, and group C (no vitamin) receiving no vitamin. General information was collected by questionnaire and thyroid function was determined in the third trimester of pregnancy. Depression was assessed 1 month postpartum by the Edinburgh postnatal depression scale (EPDS). The results showed that there was no significant difference in thyroid-stimulating hormone (TSH) level among the three groups (P > 0.05). FT₄ concentration was significantly lower in group A (n = 234: 10.68 pmol/L) than in group B (n = 220: 11.47 pmol/L) and group C (n = 195: 11.64 pmol/L) (P < 0.05), However, it was still within the normal range. EPDS scores obtained from group B (3.50) and group C (3.00) were similar but markedly lower than group A (5.00) (P < 0.05). Despite the difference in the EPDS score, the prevalence of postpartum depression was not significantly different among the three groups. In conclusion, 150 μg/day iodine supplementation for pregnant women in areas with adequate iodine had little effect on thyroid function in the third trimester, and serum FT₄ level could not be increased. Iodine supplementation during pregnancy also had no significant effect on postpartum depression.

Neonatal thyroid-stimulating hormone and association with attention-deficit/hyperactivity disorder

BACKGROUND

Normal brain development is dependent on maternal, fetal and neonatal thyroid function. Measuring neonatal thyroid-stimulating hormone (TSH) 48-72 hours after birth screens for congenital hypothyroidism, allowing early treatment to avoid serious impairment. However, even within sub-clinical ranges, disrupted thyroid homeostasis during brain development has been linked to adverse neurodevelopmental outcomes, including attention-deficit/hyperactivity disorder (ADHD).

OBJECTIVES

To estimate the association between neonatal TSH below threshold for potential congenital hypothyroidism and subsequent ADHD diagnosis using a population-based birth cohort.

METHODS

Children with a diagnosis of ADHD in the Norwegian Mother, Father and Child Cohort Study (MoBa) were identified through linkage with the Norwegian Patient Registry using ICD-10 codes for hyperkinetic disorders. The study included 405 ADHD cases and 1,092 controls (born 2003-2008) with available neonatal TSH concentrations below 10 mU/L (cut-off for potential congenital hypothyroidism) measured in dried blood spots sampled 48-72 hours after birth.

RESULTS

In multivariable, quintile models the relationship appeared to follow a U-shaped pattern with elevated odds ratios (OR) at lower and higher TSH levels. Among children with TSH in the lowest quintile, odds of ADHD was approximately 1.5-fold higher than children in the middle quintile (OR 1.60, 95% CI 1.09, 2.34), which was driven by substantially elevated risk among girls, with no association among boys (P_interaction = 0.02; girls OR 3.10, 95% CI 1.53, 6.30; boys OR 1.16, 95% CI 0.73, 1.84).

CONCLUSIONS

ADHD risk appeared to be elevated among newborns with low TSH levels (i.e. with hyperthyroid status), and this association was mainly found among girls. Because our findings are suggestive of increased risk at very low TSH concentrations, where analytical accuracy is low, future studies should employ highly sensitive assays capable of accurate quantitation at very low concentrations. Also, larger studies are needed to investigate these associations at higher neonatal TSH concentrations where data are more widely distributed.

Association of placental concentrations of phenolic endocrine disrupting chemicals with cognitive functioning in preschool children from the Environment and Childhood (INMA) Project

Developmental exposure to bisphenol A (BPA) and other phenolic endocrine disrupting chemicals (EDCs) may affect child neurodevelopment, but data on the effects of prenatal exposure to phenols on cognitive function remain sparse. Our aim was to examine the association of placental concentrations of several phenolic EDCs, including BPA, parabens (PBs), and benzophenones (BzPs), with cognitive development in preschool children from the Environment and Childhood (INMA) Project in Spain. Concentrations of BPA, four PBs (methylparaben [MePB], ethylparaben [EtPB], propylparaben [PrPB], and butylparaben [BuPB]), and six BzPs (BzP-1, BzP-2, BzP-3, BzP-6, BzP-8, and 4-hydroxybenzophenone [4-OH-BzP]) were measured in 490 placenta samples randomly selected from five INMA cohorts collected between 2000 and 2008. Neuropsychological assessment of cognitive and motor function was performed with the McCarthy Scales of Children's Abilities (MSCA) at the age of 4-5 years. Associations were assessed in a sub-sample of 191 mother-child pairs using linear and logistic regression models adjusted for confounding factors. PB compounds were detected in more than 71% of placentas, BPA in 62%, 4-OH-BzP in 50%, and the remaining BzPs in <9% of the samples. Because of the low detection frequency of BzP compounds, only 4-OH-BzP was included in the exposure-outcome analyses. After adjustment for confounders, BPA was associated with greater odds of scoring lower (below the 20th percentile) in the verbal (third vs. first exposure tertile: odds ratio [OR] = 2.78, 95% confidence interval [CI] = 1.00; 5.81, p-trend = 0.05) and gross motor (detected vs. undetected: OR = 1.75, 95%CI = 1.06; 9.29) areas, and these associations were only significant for boys. Regarding PB compounds, PrPB was associated with lower scores in memory (detected vs. undetected: β = -4.96, 95%CI = -9.54; -0.31), span memory (OR = 2.50, 95%CI = 0.95; 6.92 and 2.71, 95%CI = 0.97; 6.64, respectively for second and third tertiles, p-trend = 0.03), and motor function (β = -5.15, 95%CI = -9.26; -0.01 for third vs. first exposure tertile, p-trend = 0.04). EtPB and total PBs concentrations in the second tertile were also associated with poorer visual function of posterior cortex and worse quantitative performance, respectively, but linear trends were not statistically significant. The associations of BPA and PrPB with poorer verbal, memory, and motor skills are novel observations that warrant further attention. Larger prospective studies are required to confirm whether prenatal exposure to BPA and other phenolic EDCs is associated with impaired cognitive development.

Management of overt hypothyroidism during pregnancy

Overt hypothyroidism is a common endocrine disorder affecting 1-2% of women of reproductive age. Optimizing treatment in pregnant women with overt hypothyroidism can reduce adverse fetal and maternal outcomes. Ideally, women who are known to have a history of hypothyroidism or those with risk factors for becoming hypothyroid, should have adequate preconception care to ensure euthyroidism from the onset of pregnancy, with a TSH target of below 2.5mIU/L. On women who are already on levothyroxine, an empirical dose increase of 30-50% as soon as pregnancy is confirmed may be considered. During pregnancy, levothyroxine doses should be titrated against TSH, which have trimester-specific ranges. In women who are known to be hypothyroid but are inadequately treated, we recommend a doubling of levothyroxine dose on at least three days a week to rapidly achieve euthyroidism. In newly diagnosed overt hypothyroidism in pregnancy, starting doses of either 100 or 150 mg daily may be considered safe.