Maternal and Child's Thyroid Function and Child's Intellect and Scholastic Performance

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.

Maternal thyroid hormone receptor β activation in mice sparks brown fat thermogenesis in the offspring

It is well established that maternal thyroid hormones play an important role for the developing fetus; however, the consequences of maternal hyperthyroidism for the offspring remain poorly understood. Here we show in mice that maternal 3,3',5-triiodothyronine (T3) treatment during pregnancy leads to improved glucose tolerance in the adult male offspring and hyperactivity of brown adipose tissue (BAT) thermogenesis in both sexes starting early after birth. The activated BAT provides advantages upon cold exposure, reducing the strain on other thermogenic organs like muscle. This maternal BAT programming requires intact maternal thyroid hormone receptor β (TRβ) signaling, as offspring of mothers lacking this receptor display the opposite phenotype. On the molecular level, we identify distinct T3 induced alterations in maternal serum metabolites, including choline, a key metabolite for healthy pregnancy. Taken together, our results connect maternal TRβ activation to the fetal programming of a thermoregulatory phenotype in the offspring.

Maternal Thyroid Function During Pregnancy and Offspring White Matter Microstructure in Early Adulthood: A Prospective Birth Cohort Study

Background: The fetus is fully dependent on maternal thyroid hormones until mid-gestation and suboptimal maternal thyroid function has been associated with alterations in the neurodevelopment of the offspring. We used maternal free thyroxine (fT4) and thyrotropin (TSH) levels in early gestation to study the association of maternal thyroid function during early pregnancy and offspring brain white matter (WM) integrity in early adulthood. Methods: Our study population consisted of a total of 292 mother-child pairs. Maternal fT4 and TSH were used as predictors and offspring multimodal imaging measures of fractional anisotropy, mean diffusivity, and magnetization transfer ratio (FA, MD, and MTR) as dependent variables. First, as Global analysis, all analyzed 14 WM tracts were studied simultaneously using linear-mixed effect models. Second, if a global effect was detected, a post hoc Tract-wise analysis was carried out using linear models individually in each WM tract. Study population was stratified by sex. Results: We found a positive association between maternal fT4 and offspring Global FA in males when adjusted for all maternal and offspring covariates (n = 114; β = 0.154; confidence interval = 0.045-0.263; p = 0.006). The finding was observed to be driven by multiple WM tracts, of which three projection fiber tracts and the forceps minor survived correcting for multiple comparisons in Tract-wise analysis. Conclusions: Maternal thyroid function in early pregnancy was observed to be associated with WM microstructure in male offspring in early adulthood. Our results suggest that maternal fT4 levels in early pregnancy may modulate axonal characteristics, with a long-term effect on offspring WM development.

Treatment of recurrent pregnancy loss in women with euthyroid-based thyroid peroxidase antibody syndrome

Recurrent pregnancy loss (RPL) due to thyroid peroxidase antibody (TPOAb) syndrome remains a significant challenge in pregnancy. The current study offers better insights into miscarriages that occur due to the presence of TPOAb with euthyroid in pregnant women with a history of RPL. Out of the 347 women confirmed with unexplained RPL, only 70 (20.2%) tested positive for TPOAb (215±53). After eight women were excluded from the study due to failure to follow up, 62 participants (age range: 33±4.8 years; body mass index (BMI):25-30kg/m2 (58%) and >30kg/m2 (42%)) were included. The TPOAb-dependent RPL patients were divided according to their RPL types into 23 (30.7%) nulliparous (1˚) and 39 (69.3%) multiparous (2˚) patients, respectively. Out of the sample, 69.2% and 30.8% had a history of miscarriages during the 1st and 2nd trimesters, respectively. For treatment purposes, while screening for the TPOAb, the women received 50µg/day of L-thyroxine (LTx) for three months prior to pregnancy and during the first three months of pregnancy and were followed up until giving birth or miscarriage. Thyroxine treatment was correlated to successful normal births in 56.6% and 21.2% of pregnant women after 36 and during 28-36 weeks of gestation, respectively. However, miscarriages occurred in 18.1% and 4.1% of patients during 14-28 weeks and before 14 weeks of gestation, respectively. The current findings show the promising use of thyroxine in the control of RPL caused by euthyroid-based thyroid peroxidase antibody syndrome. This treatment has led to a significant number of women experiencing successful full-term pregnancies and giving birth to healthy babies.

Association of perchlorate, thiocyanate, and nitrate with dyslexic risk

Perchlorate, thiocyanate, and nitrate are sodium iodide symporter (NIS) inhibitors that disturb iodide uptake into the thyroid and have been implicated in child development. However, no data are available on the association between exposure to/related with them and dyslexia. Here, we examined the association of exposure to/related with the three NIS inhibitors with the risk of dyslexia in a case-control study. The three chemicals were detected in urine samples of 355 children with dyslexia and 390 children without dyslexia from three cities in China. The adjusted odds ratios for dyslexia were examined using logistic regression models. The detection frequencies of all the targeted compounds were 100%. After adjusting for multiple covariates, urinary thiocyanate was significantly associated with the risk of dyslexia (P-trend = 0.02). Compared with the lowest quartile, children within the highest quartile had a 2.66-fold risk of dyslexia (95% confidence interval: 1.32, 5.36]. Stratified analyses showed that the association between urinary thiocyanate level and the risk of dyslexia was more pronounced among boys, children with fixed reading time, and those without maternal depression or anxiety during pregnancy. Urinary perchlorate and nitrate levels were not associated with the risk of dyslexia. This study suggests the possible neurotoxicity of thiocyanate or its parent compounds in dyslexia. Further investigation is warranted to confirm our findings and clarify the potential mechanisms.

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".

Effects of choline supplementation in mothers with hypothyroidism on the brain-derived neurotrophic factor gene expression changes in pre-pubertal offspring rats

BACKGROUND

Thyroid hormones play a vital function in the maturation in the course of mind development. Regarding the well-known effects of choline on brain-derived neurotrophic factor (BDNF), the study examined the effects of choline on hippocampal BDNF gene expression in maternal hypothyroidism rats.

METHODS AND RESULTS

To induce the hypothyroidism, 6-propyl-2-thiouracil was introduced to the ingesting water from the sixth day of gestation to twenty-first postnatal day (PND). Choline-treatment started twice a day on the first day of gestation until PND 21. On PND28, pups were sacrificed. The expression of BDNF gene was evaluated after the hippocampus was harvested. Our results demonstrated that both male and female pre-pubertal offspring rats' BDNF gene expression was decreased by developmental hypothyroidism. Choline increases the ratio of relative gene expression of BDNF in the hippocampus of males and females in the control/hypothyroidism group, especially in males.

CONCLUSIONS

It can be concluded that maternal choline supplementation on the first day of gestation until PND 21 improves brain development and cognitive function in pre-pubertal offspring rats regarding control/hypothyroidism groups.

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.

Persistent Organic Pollutant Exposure and Thyroid Function among 12-Year-Old Children

INTRODUCTION

Polychlorobiphenyls (PCBs), organochlorine pesticides (OCPs), and per- and polyfluoroalkyl substances (PFASs) are persistent organic pollutants (POPs) having numerous toxicological properties, including thyroid endocrine disruption. Our aim was to assess the impact of POPs on thyroid hormones among 12-year-old children, while taking puberty into consideration.

METHODS

Exposure to 7 PCBs, 4 OCPs, and 6 PFASs (in µg/L), and free tri-iodothyronine (fT3, pg/mL), free thyroxine (fT4, ng/dL), and thyroid-stimulating hormones (TSH, mIU/L) were assessed through blood-serum measurements at age 12 years in 249 boys and 227 girls of the PELAGIE mother-child cohort (France). Pubertal status was clinically rated using the Tanner stages. For each POP, associations were estimated using linear regression, adjusted for potential confounders.

RESULTS

Among boys, hexachlorobenzene and perfluorodecanoic acid were associated with decreased fT3 (log-scale; β [95% confidence interval] = -0.07 [-0.12,-0.02] and β = -0.03 [-0.06,-0.00], respectively). Intermediate levels of perfluorohexanesulfonic acid (PFHxS) and PCB180 were associated, respectively, with increased and decreased fT4. After stratification on pubertal status, PCBs and OCPs were associated with decreased TSH only in the more advanced Tanner stages (3-5) and with decreased fT3 among early Tanner stages (1-2). Among girls, PFHxS was associated with decreased TSH (log-scale; β = -0.15 [-0.29,-0.00]), and perfluorooctanoic acid was associated with decreased fT3 (β2nd_tercile = -0.06 [-0.10,-0.03] and β3rd_tercile = -0.04 [-0.08,-0.00], versus. 1st tercile).

DISCUSSION

This cross-sectional study highlights associations between some POPs and thyroid function disruption, which appears consistent with the literature. Considering that the associations were sex-specific and moderated by pubertal status in boys, complex endocrine interactions are likely involved.

Evaluating thyroid function in pregnant women

Thyroid hormones are primarily responsible for regulating the basal metabolic rate but also make important contributions to reproductive function and fetal development. Both hyper- and hypothyroidism in pregnancy have been associated with increased risks of complications that include preeclampsia and low birth weight, among others. Furthermore, thyroid hormone deficiency in the developing fetus results in neurodevelopmental delay. As the fetus is exclusively reliant on maternal thyroid hormone for most of the first trimester and requires continued maternal supply until birth, identifying maternal thyroid dysfunction is critically important. However, evaluating thyroid function in pregnancy is challenging because of the many physiological changes that affect concentrations of thyroid-related analytes. Increasing plasma human chorionic gonadotropin (hCG) concentrations in the second half of the first trimester elicit a corresponding transient decrease in thyroid-stimulating hormone (TSH), and continually increasing estradiol concentrations throughout pregnancy cause substantial increases in thyroxine-binding globulin (TBG) and total thyroxine (T4) relative to the nonpregnant state. Lastly, free T4 concentrations gradually decrease with increasing gestational age. For these reasons, it is essential to interpret thyroid function test results in the context of trimester-specific reference intervals to avoid misclassification of thyroid status. This review summarizes the effects of thyroid dysfunction prior to conception and during pregnancy and describes considerations for the laboratory assessment of thyroid function in pregnant women.

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.

Towards a science-based testing strategy to identify maternal thyroid hormone imbalance and neurodevelopmental effects in the progeny-part III: how is substance-mediated thyroid hormone imbalance in pregnant/lactating rats or their progeny related to neurodevelopmental effects?

This review investigated which patterns of thyroid- and brain-related effects are seen in rats upon gestational/lactational exposure to 14 substances causing thyroid hormone imbalance by four different modes-of-action (inhibition of thyroid peroxidase, sodium-iodide symporter and deiodinase activities, enhancement of thyroid hormone clearance) or to dietary iodine deficiency. Brain-related parameters included motor activity, cognitive function, acoustic startle response, hearing function, periventricular heterotopia, electrophysiology and brain gene expression. Specific modes-of-action were not related to specific patterns of brain-related effects. Based upon the rat data reviewed, maternal serum thyroid hormone levels do not show a causal relationship with statistically significant neurodevelopmental effects. Offspring serum thyroxine together with offspring serum triiodothyronine and thyroid stimulating hormone appear relevant to predict the likelihood for neurodevelopmental effects. Based upon the collated database, thresholds of ≥60%/≥50% offspring serum thyroxine reduction and ≥20% and statistically significant offspring serum triiodothyronine reduction indicate an increased likelihood for statistically significant neurodevelopmental effects; accuracies: 83% and 67% when excluding electrophysiology (and gene expression). Measurements of brain thyroid hormone levels are likely relevant, too. The extent of substance-mediated thyroid hormone imbalance appears more important than substance mode-of-action to predict neurodevelopmental impairment in rats. Pertinent research needs were identified, e.g. to determine whether the phenomenological offspring thyroid hormone thresholds are relevant for regulatory toxicity testing. The insight from this review shall be used to suggest a tiered testing strategy to determine whether gestational/lactational substance exposure may elicit thyroid hormone imbalance and potentially also neurodevelopmental effects.

Cord Blood Thyroid Hormones and Neurodevelopment in 2-Year-Old Boys and Girls

Objective: Thyroid hormones are essential for neurodevelopment in early life. However, the impact of mild alterations in neonatal thyroid hormones on infant neurodevelopment and its sex dimorphism is unclear. We aimed to assess whether mild variations in neonatal thyroid hormones of term-born newborns with maternal euthyroid are related to neurodevelopment in 2-year-old boys and girls.

Methods: This study used data from 452 singleton term-born infants of mothers with normal thyroid function in Shanghai, China, and their follow-up measure at the age of 2 years. Cord serum concentrations of free thyroxine (FT4), free triiodothyronine (FT3), thyroid-stimulating hormone (TSH), and thyroid peroxidase antibody (TPOAb) were measured by chemiluminescent microparticle immunoassays and classified into three groups: the low (1st, Q1), middle (2nd−4th, Q2–Q4), and high (5th, Q5) quintiles. Neurodevelopment indices were assessed using the Ages and Stages Questionnaire, third edition (ASQ-3), at 24 months of age.

Results: Compared to infants with thyroid hormones in the middle (Q2–Q4), boys with FT4 in the lowest quintile had 5.08 (95% CI: 1.37, 8.78) points lower scores in the communication domain, 3.25 (0.25,6.25) points lower scores in the fine motor domain, and 3.84 (0.04, 7.64) points lower scores in the personal-social domain, respectively. Boys with FT3 in the highest quintile had 4.46 (0.81, 8.11) points increase in the personal-social domain. These associations were not observed in girls. No associations were observed between cord blood serum TSH and ASQ-assessed neurodevelopment in the boys or the girls.

Conclusions: Mild alterations in thyroid hormones of newborns were associated adversely with neurodevelopment in boys, suggesting the importance of optimal thyroid hormone status for neurodevelopment in early life.

Associations Between Maternal Prenatal C-Reactive Protein and Risk Factors for Psychosis in Adolescent Offspring: Findings From the Northern Finland Birth Cohort 1986

Prenatal infection is associated with brain structural and functional abnormalities and may increase the risk for psychosis through a direct effect on neurodevelopment. Various infections may exert their effect through a proinflammatory immune response but studies of prenatal maternal inflammatory markers and offspring neurodevelopment are scarce. Using the longitudinal Northern Finland Birth Cohort 1986 study, we examined the associations of maternal prenatal C-reactive protein (CRP) levels with psychosis risk factors in adolescent offspring. CRP was measured in maternal sera collected in pregnancy. In offspring, school performance was measured at age 7 years, while school performance, psychotic experiences, and cannabis use were measured at age 16 years. We tested associations of CRP with offspring measures using regression analysis controlling for offspring sex, maternal education level, and prenatal maternal body mass index, smoking and alcohol use in pregnancy, place of birth, maternal psychiatric admission, paternal psychiatric admission, mothers age at birth, and gestational week of CRP sample. We also tested if adolescent cannabis use mediated the associations between maternal CRP and offspring outcomes. Controlling for covariates, maternal CRP was associated with academic performance at age 16 years (beta = .062, 95% CI = 0.036-0.088), but not with possible psychotic experiences at 16 years (odds ratio [OR] = 1.09, 95% CI = 0.96-1.24). Maternal CRP was also associated with adolescent cannabis use (OR = 1.24, 95% CI = 1.07-1.43). These findings suggest that prenatal inflammation may influence later mental illness risk by affecting neurodevelopment and also indirectly by increasing the risk of exposure to cannabis.

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.

Indications for treatment of subclinical hypothyroidism and isolated hypothyroxinaemia in pregnancy

Thyroid hormones are essential for maintaining a pregnancy and optimal fetal neurological development. Pregnancy places additional demands on the thyroid axis and around 5% of women who have their thyroid function checked during gestation will have borderline low thyroid function (subclinical hypothyroidism or isolated hypothyroxinemia) identified. These borderline low thyroid states are associated with adverse obstetric and offspring outcomes. Whilst it is well established that overt hypothyroidism requires treatment with levothyroxine, it is less clear whether there is any benefit of treating borderline low thyroid states. This review summarizes the potential indications for treatment of subclinical hypothyroidism and isolated hypothyroxinemia.

Systemic endocrinopathies (thyroid conditions and diabetes): impact on postnatal life of the offspring

Fetal programming may influence childhood and adult life, determining the risk of specific diseases. During earlier stages of pregnancy, the transfer of maternal thyroid hormones to the fetus is vital for adequate neurologic development. The presence of severe maternal thyroid dysfunction, particularly severe iodine deficiency, is devastating, leading to irreversible neurologic sequelae. Moreover, mild maternal thyroid conditions, such as a mild-to-moderate iodine deficiency, may also lead to milder neurologic and behavioral conditions later during the life of the offspring. Maternal dysglycemia due to pregestational or gestational diabetes mellitus is another common situation in which fetal development encounters a hostile environment. Hyperglycemia in utero may trigger metabolic conditions in the offspring, including abnormalities of glucose tolerance and weight excess. Physicians assisting pregnant women have to be aware about these conditions, because they may go unnoticed if not properly screened. Because an early diagnosis and appropriate management may prevent most of the possible negative consequences for the progeny, the prevention, early diagnosis, and proper management of these endocrine conditions should be offered to all women undergoing pregnancy. Here, we comprehensively review the current evidence about the effects of maternal thyroid dysfunction and maternal dysglycemia on the cognitive function and carbohydrate metabolism in the offspring, two prevalent conditions of utmost importance for the child's health and development.

[Thyroid hormones regulate neural stem cell fate]

Thyroid hormones (THs) are vital for vertebrate brain function throughout life, from early development to ageing. Epidemiological studies show an adequate supply of maternal TH during pregnancy to be necessary for normal brain development, and this from the first trimester of onwards. Maternal TH deficiency irreversibly affects fetal brain development, increasing the risk of offspring cognitive disorders and IQ loss. Mammalian and non-mammalian (zebrafish, xenopus, chicken) models are useful to dissect TH-dependent cellular and molecular mechanisms governing embryonic and fetal brain development: a complex process including cell proliferation, survival, determination, migration, differentiation and maturation of neural stem cells (NSCs). Notably, rodent models have strongly contributed to understand the key neurogenic roles of TH still at work in adult life. Neurogenesis continues in two main areas, the sub-ventricular zone lining the lateral ventricles (essential for olfaction) and the sub-granular zone in the dentate gyrus of the hippocampus (involved in memory, learning and mood control). In both niches, THs tightly regulate the balance between neurogenesis and oligodendrogenesis under physiological and pathological contexts. Understanding how THs modulate NSCs determination toward a neuronal or a glial fate throughout life is a crucial question in neural stem cell biology. Providing answers to this question can offer therapeutic strategies for brain repair, notably in neurodegenerative diseases, demyelinating diseases or stroke where new neurons and/or oligodendrocytes are required. The review focuses on TH regulation of NSC fate in mammals and humans both during development and in the adult.

A transient window of hypothyroidism alters neural progenitor cells and results in abnormal brain development

Cortical heterotopias are clusters of ectopic neurons in the brain and are associated with neurodevelopmental disorders like epilepsy and learning disabilities. We have previously characterized the robust penetrance of a heterotopia in a rat model, induced by thyroid hormone (TH) disruption during gestation. However, the specific mechanism by which maternal TH insufficiency results in this birth defect remains unknown. Here we first determined the developmental window susceptible to endocrine disruption and describe a cellular mechanism responsible for heterotopia formation. We show that five days of maternal goitrogen treatment (10 ppm propylthiouracil) during the perinatal period (GD19-PN2) induces a periventricular heterotopia in 100% of the offspring. Beginning in the early postnatal brain, neurons begin to aggregate near the ventricles of treated animals. In parallel, transcriptional and architectural changes of this region were observed including decreased Sonic hedgehog (Shh) expression, abnormal cell adhesion, and altered radial glia morphology. As the ventricular epithelium is juxtaposed to two sources of brain THs, the cerebrospinal fluid and vasculature, this progenitor niche may be especially susceptible to TH disruption. This work highlights the spatiotemporal vulnerabilities of the developing brain and demonstrates that a transient period of TH perturbation is sufficient to induce a congenital abnormality.

Maternal Thyroid Function During Pregnancy or Neonatal Thyroid Function and Attention Deficit Hyperactivity Disorder: A Systematic Review

BACKGROUND

Attention deficit hyperactivity disorder (ADHD) is the most common neurobehavioral disorder in children, yet its etiology is poorly understood. Early thyroid hormone disruption may contribute to the development of ADHD. Disrupted maternal thyroid hormone function has been associated with adverse neurodevelopmental outcomes in children. Among newborns, early-treated congenital hypothyroidism has been consistently associated with later cognitive deficits.

METHODS

We systematically reviewed literature on the association between maternal or neonatal thyroid hormones and ADHD diagnosis or symptoms. We searched Embase, Pubmed, Cinahl, PsycInfo, ERIC, Medline, Scopus, and Web of Science for articles published or available ahead of print as of April 2018.

RESULTS

We identified 28 eligible articles: 16 studies of maternal thyroid hormones, seven studies of early-treated congenital hypothyroidism, and five studies of neonatal thyroid hormones. The studies provide moderate evidence for an association between maternal thyroid hormone levels and offspring ADHD, some evidence for an association between early-treated congenital hypothyroidism and ADHD, and little evidence for an association between neonatal thyroid hormone levels and later ADHD.

CONCLUSIONS

The reviewed articles suggest an association between maternal thyroid function and ADHD, and possibly between early-treated congenital hypothyroidism and ADHD. Study limitations, however, weaken the conclusions in our systematic review, underlining the need for more research. Importantly, there was much variation in the measurement of thyroid hormone function and of ADHD symptoms. Recommendations for future research include using population-based designs, attending to measurement issues for thyroid hormones and ADHD, considering biologically relevant covariates (e.g., iodine intake), and assessing nonlinear dose-responses.

Thyroid function in neonates of women with subclinical hypothyroidism or hypothyroxinemia

OBJECTIVE

To assess whether treatment of pregnant women with subclinical hypothyroidism or hypothyroxinemia alters neonatal TSH results.

STUDY DESIGN

A planned secondary analysis of data from two multi-center randomized, double-masked, placebo-controlled thyroxine replacement trials in pregnant women with either subclinical hypothyroidism or hypothyroxinemia. Infant heel-stick specimens were obtained before discharge. We compared TSH levels between neonates born to mothers allocated to treatment or placebo within each trial and between neonates in the placebo groups. Multiples of means were generated for day-of-life-specific data.

RESULTS

Neonatal TSH values were available for 573/677 (84.6%) newborns from the subclinical hypothyroidism trial and 461/526 (87.6%) newborns from the hypothyroxinemia trial. Neonatal TSH values did not differ in either trial by treatment group or between placebo groups (P > 0.05 for all comparisons).

CONCLUSIONS

Neonatal TSH values did not differ with thyroid hormone replacement in pregnancies diagnosed with subclinical hypothyroidism or hypothyroxinemia.

The impact of gestational hypothyroxinemia on the cognitive and motor development of offspring

In the past decade, it is still controversial whether gestational hypothyroxinemia has adverse effects on fetal brain development. Animal models of maternal hypothyroxinemia have proved that thyroid hormone is necessary for the adequate development of a number of neuropsychological abilities whereas the type of deficit depends on the timing of thyroid hormone (TH) deficiency. However, different from animal experiments, evidence from clinical trials showed that the major determinant of mental and motor function delay in offspring is the gestational age at onset of maternal hypothyroxinemia. The correlation between levels of maternal FT4 in the first trimester and impaired neurodevelopment in offspring is strongest. With the progress of pregnancy, the correlation weakened gradually and disappeared until late pregnancy. Only two studies involving randomized controlled trials have examined the treatment of hypothyroxinemia with levothyroxine in pregnancy. However, both randomized trials were started too late in gestation to have a major influence on brain development.

Prevalence of subclinical hypothyroidism in pregnancy in Saudi Arabia

objectives:

To estimate the prevalence of subclinical hypothyroidism (SCH) in Saudi Arabia and assess the need for an SCH screening program.

Methods:

This cross-sectional study was conducted at King Abdulaziz Medical City and the Khashmulaan Clinic at the National Guard Health Affairs, Riyadh, Saudi Arabia in August 2016. All women attending the antenatal clinics were invited to participate in the study. In addition, data were retrieved from the files of pregnant women who had been screened for hypothyroidism from January 2016 to August 2016. A total of 384 pregnant women were included in the study.

Results:

The prevalence of SCH in pregnant women in this study was 50/384 (13%) with 95% confidence intervals (CIs): 9.82%-16.80%. Pregnant women who were randomly screened using a survey (n=127) were 3 times more likely (OR: 3.1; 95% CI: 1.182 to 8.704, p=0.022) to have SCH compared to pregnant women who were screened based on their physician’s judgement (n=257). Results showed older age (≥40 years) was associated with an insignificant decrease in the risk of SCH.

Conclusion:

Random screening for SCH in pregnant women showed a higher prevalence in comparison to women who were screened as a result of physician referrals. The results highlight the urgent need for larger studies to investigate the prevalence of SCH as well as the need for an SCH screening program.

Graves' disease and pregnancy

This section deals with the specificities of managing Graves' disease during pregnancy. Graves' disease incurs risks of fetal, neonatal and maternal complications that are rare but may be severe: fetal hyper- or hypothyroidism, usually first showing as fetal goiter, neonatal dysthyroidism, premature birth and pre-eclampsia. Treatment during pregnancy is based on antithyroid drugs alone, without association to levothyroxine. An history of Graves' disease, whether treated radically or not, with persistent maternal anti-TSH-receptor antibodies must be well identified. Fetal monitoring should be initiated in a multidisciplinary framework that should be continued throughout pregnancy. Neonatal monitoring is also crucial if the mother still shows anti-TSH-receptor antibodies at end of pregnancy or underwent antithyroid treatment. The risk of recurrence of hyperthyroidism in the weeks following delivery requires maternal monitoring. The long-term neuropsychological progression of children of mothers with Graves' disease is poorly known.

Food Additives and Child Health

Increasing scientific evidence suggests potential adverse effects on children's health from synthetic chemicals used as food additives, both those deliberately added to food during processing (direct) and those used in materials that may contaminate food as part of packaging or manufacturing (indirect). Concern regarding food additives has increased in the past 2 decades in part because of studies that increasingly document endocrine disruption and other adverse health effects. In some cases, exposure to these chemicals is disproportionate among minority and low-income populations. This report focuses on those food additives with the strongest scientific evidence for concern. Further research is needed to study effects of exposure over various points in the life course, and toxicity testing must be advanced to be able to better identify health concerns prior to widespread population exposure. The accompanying policy statement describes approaches policy makers and pediatricians can take to prevent the disease and disability that are increasingly being identified in relation to chemicals used as food additives, among other uses.

Clinical associations of maternal thyroid function with foetal brain development: Epidemiological interpretation and overview of available evidence

Thyroid hormone is an important regulator of early brain development, particularly during early stages of gestation during which foetal thyroid hormone availability depends on the maternal transfer of thyroid hormones. There is a wide range of experimental studies showing that low maternal thyroid hormone availability is associated with suboptimal brain development parameters. While few clinical studies have shown that overt maternal hypothyroidism is associated with lower child IQ, the question whether more subclinical changes in maternal thyroid function could also lead to suboptimal foetal brain development. In this review, we put the latter studies in perspective and discuss their interpretation from an epidemiological and clinical perspective. Furthermore, we extend this discussion to also include future perspective and identify important knowledge gaps in the field.

Subclinical Hypothyroidism in Women Planning Conception and During Pregnancy: Who Should Be Treated and How?

Subclinical hypothyroidism (SCH), a mild form of hypothyroidism defined as elevated TSH with normal free thyroxine levels, is a common diagnosis among women of reproductive age. In some, but not all, studies, it has been associated with infertility, an increased risk of adverse pregnancy and neonatal outcomes, and possibly with an increased risk of neurocognitive deficits in offspring. Despite well-established recommendations on treatment of overt hypothyroid pregnant women, a consensus has not yet been reached on whether to treat women with SCH. This review focuses on examining the evidence informing the clinical strategy for using levothyroxine (LT4) in women with SCH during pregnancy and those who are planning conception. A crucial first step is to accurately diagnose SCH using the appropriate population-based reference range. For pregnant women, if this is unavailable, the recommended TSH upper normal limit cutoff is 4.0 mIU/L. There is evidence supporting a decreased risk for pregnancy loss and preterm delivery for pregnant women with TSH > 4.0 mIU/L receiving LT4 therapy. LT4 treatment has been associated with better reproductive outcomes in women with SCH undergoing artificial reproductive techniques, but not in those who are attempting natural conception. Thyroid function tests need to be repeated throughout pregnancy to monitor LT4 therapy. In addition to potential harms, LT4 contributes to treatment burden. During a consultation, clinicians and patients should engage in a careful consideration of the current evidence in the context of the patients’ values and preferences to determine whether LT4 therapy initiation is the best next step.

Maternal thyroid hormone insufficiency during pregnancy and risk of neurodevelopmental disorders in offspring: A systematic review and meta-analysis

BACKGROUND

In the last 2 decades, several studies have examined the association between maternal thyroid hormone insufficiency during pregnancy and neurodevelopmental disorders in children and shown conflicting results.

AIM

This systematic review aimed to assess the evidence for an association between maternal thyroid hormone insufficiency during pregnancy and neurodevelopmental disorders in children. We also sought to assess whether levothyroxine treatment for maternal thyroid hormone insufficiency improves child neurodevelopment outcomes.

METHODS

We performed systematic literature searches in MEDLINE, EMBASE, PSYCinfo, CINAHL, AMED, BNI, Cochrane, Scopus, Web of Science, GreyLit, Grey Source and Open Grey (latest search: March 2017). We also conducted targeted web searching and performed forwards and backwards citation chasing. Meta-analyses of eligible studies were carried out using the random-effects model.

RESULTS

We identified 39 eligible articles (37 observational studies and 2 randomized controlled trials [RCT]). Meta-analysis showed that maternal subclinical hypothyroidism and hypothyroxinaemia are associated with indicators of intellectual disability in offspring (odds ratio [OR] 2.14, 95% confidence interval [CI] 1.20 to 3.83, P = .01, and OR 1.63, 95% CI 1.03 to 2.56, P = .04, respectively). Maternal subclinical hypothyroidism and hypothyroxinaemia were not associated with attention deficit hyperactivity disorder, and their effect on the risk of autism in offspring was unclear. Meta-analysis of RCTs showed no evidence that levothyroxine treatment for maternal hypothyroxinaemia or subclinical hypothyroidism reduces the incidence of low intelligence quotient in offspring.

LIMITATIONS

Although studies were generally of good quality, there was evidence of heterogeneity between the included observational studies (I² 72%-79%).

CONCLUSION

Maternal hypothyroxinaemia and subclinical hypothyroidism may be associated with intellectual disability in offspring. Currently, there is no evidence that levothyroxine treatment, when initiated 8- to 20-week gestation (mostly between 12 and 17 weeks), for mild maternal thyroid hormone insufficiency during pregnancy reduces intellectual disability in offspring.

Maternal thyroid function and child educational attainment: prospective cohort study

OBJECTIVE

To determine if first trimester maternal thyroid dysfunction is a critical determinant of child scholastic performance and overall educational attainment.

DESIGN

Prospective cohort study.

SETTING

Avon Longitudinal Study of Parents and Children cohort in the UK.

PARTICIPANTS

4615 mother-child pairs with an available first trimester sample (median 10 weeks gestation, interquartile range 8-12).

EXPOSURES

Free thyroxine, thyroid stimulating hormone, and thyroid peroxidase antibodies assessed as continuous measures and the seven clinical categories of maternal thyroid function.

MAIN OUTCOME MEASURES

Five age-specific national curriculum assessments in 3580 children at entry stage assessment at 54 months, increasing up to 4461 children at their final school assessment at age 15.

RESULTS

No strong evidence of clinically meaningful associations of first trimester free thyroxine and thyroid stimulating hormone levels with entry stage assessment score or Standard Assessment Test scores at any of the key stages was found. Associations of maternal free thyroxine or thyroid stimulating hormone with the total number of General Certificates of Secondary Education (GCSEs) passed (range 0-16) were all close to the null: free thyroxine, rate ratio per pmol/L 1.00 (95% confidence interval 1.00 to 1.01); and thyroid stimulating hormone, rate ratio 0.98 (0.94 to 1.02). No important relationship was observed when more detailed capped scores of GCSEs allowing for both the number and grade of pass or when language, mathematics, and science performance were examined individually or when all educational assessments undertaken by an individual from school entry to leaving were considered. 200 (4.3%) mothers were newly identified as having hypothyroidism or subclinical hypothyroidism and 97 (2.1%) subclinical hyperthyroidism or hyperthyroidism. Children of mothers with thyroid dysfunction attained an equivalent number of GCSEs and equivalent grades as children of mothers with euthyroidism.

CONCLUSIONS

Maternal thyroid dysfunction in early pregnancy does not have a clinically important association with impaired child performance at school or educational achievement.

The impact of isolated maternal hypothyroxinaemia on the incidence of large-for-gestational-age infants: the Ma'anshan Birth Cohort study

OBJECTIVE

The purpose of this study was to investigate whether isolated maternal hypothyroxinaemia (IMH) is associated with risks of small/large-for-gestational-age (SGA/LGA) infants.

DESIGN

Population-based prospective cohort study.

SETTING

Ma'anshan Maternal and Child Health (MCH) clinics, China.

POPULATION

Pregnant women with singleton births (n = 3178).

METHODS

Descriptive statistics were calculated for the demographic characteristics of the mothers and their newborns. Linear regression was applied to estimate the association between thyroid hormone levels and birthweight. Logistic regression was performed to calculate the association between IMH and SGA/LGA.

MAIN OUTCOME MEASURES

Outcomes included SGA/LGA.

RESULTS

The prevalence of IMH, defined as a free thyroxine value (FT4) lower than the 2.5th percentile with normal thyroid stimulating hormone, was 2.5% (78/3080) and 2.5% (74/2999) in the first and second trimesters, respectively. Additionally, 306 (9.6%) and 524 (16.5%) infants were defined as SGA and LGA, respectively. No evidence supported the notion that IMH is associated with an increased risk for SGA in either the first [odds ratio (OR): 1.762, 95% confidence interval (CI): 0.759-4.089] or the second (OR: 0.763, 95% CI: 0.231-2.516) trimester. However, an increased risk of LGA was observed among IMH women in the second trimester (OR: 2.088, 95% CI: 1.193-3.654). Maternal TPO-Ab positivity in the second trimester increased the risk of SGA (OR: 2.094, 95% CI: 1.333-3.290).

CONCLUSION

This study provides evidence that IMH is associated with LGA.

FUNDING

This work was supported by the National Natural Science Foundation of China (No. 81330068).

TWEETABLE ABSTRACT

Isolated maternal hypothyroxinaemia may increase the risk of large-for-gestational-age infants.

Comparative approaches to understanding thyroid hormone regulation of neurogenesis

Thyroid hormone (TH) signalling, an evolutionary conserved pathway, is crucial for brain function and cognition throughout life, from early development to ageing. In humans, TH deficiency during pregnancy alters offspring brain development, increasing the risk of cognitive disorders. How TH regulates neurogenesis and subsequent behaviour and cognitive functions remains a major research challenge. Cellular and molecular mechanisms underlying TH signalling on proliferation, survival, determination, migration, differentiation and maturation have been studied in mammalian animal models for over a century. However, recent data show that THs also influence embryonic and adult neurogenesis throughout vertebrates (from mammals to teleosts). These latest observations raise the question of how TH availability is controlled during neurogenesis and particularly in specific neural stem cell populations. This review deals with the role of TH in regulating neurogenesis in the developing and the adult brain across different vertebrate species. Such evo-devo approaches can shed new light on (i) the evolution of the nervous system and (ii) the evolutionary control of neurogenesis by TH across animal phyla. We also discuss the role of thyroid disruptors on brain development in an evolutionary context.

Associations between thyroid dysfunction and developmental status in children with excessive iodine status

Background and objective

Adequate iodine status and normal thyroid hormone synthesis are important for optimal child development. In this study, we explored whether young children’s developmental status is associated with thyroid dysfunction in an area of chronic excessive iodine exposure.

Methods

We included 298 children between 18 and 48 months of age residing in Algerian refugee camps. Early child development was measured using the Ages and Stages Questionnaires, third edition (ASQ-3), consisting of five domains: Communication, Gross Motor, Fine Motor, Problem Solving and Personal-Social. Due to poor discriminatory ability in the Gross Motor domain, the total ASQ-3 scores were calculated both including and excluding this domain. Urinary iodine concentration (UIC), thyroid hormones (TSH, FT3 and FT4), thyroid antibodies and serum thyroglobulin (Tg) were measured.

Results

The median UIC was 451.6 μg/L, and approximately 72% of the children had a UIC above 300 μg/L. Furthermore, 14% had thyroid disturbances, of whom 10% had TSH outside the reference range. Children with thyroid disturbances and TSH outside the reference ranges had lower odds of being among the 66% highest total ASQ scores, with adjusted odds ratios (95% CI) of 0.46 (0.23, 0.93) and 0.42 (0.19, 0.94), respectively.

Conclusion

We found an association between thyroid dysfunction and poorer developmental status among children with excessive iodine intake. The high iodine intake may have caused the thyroid dysfunction and hence the delayed developmental status; however, other influential factors cannot be excluded. Optimal child development is important for a sustainable future. With iodine excess being an increasing problem globally, this subject should be further explored.

MECHANISMS IN ENDOCRINOLOGY: Maternal thyroid dysfunction during pregnancy and behavioural and psychiatric disorders of children: a systematic review

BACKGROUND

Maternal thyroid dysfunction during pregnancy may lead to persistent neurodevelopmental disorders in the offspring appearing in later life. This study aimed to review the available evidence concerning the relationship between maternal thyroid status during pregnancy and offspring behavioural and psychiatric disorders.

METHODS

Systematic electronic database searches were conducted using PubMed, Embase, PsycNET, Scopus, Google Scholar and Cochrane library. Studies including gestational thyroid dysfunction as the exposure and offspring behavioural and psychiatric disorders as the outcome were included. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline was followed and, after thorough screening by two independent reviewers, 13 articles remained eligible for inclusion in this study.

RESULTS

Indicators of maternal thyroid dysfunction, including low and high thyroid hormone level and autoimmune thyroiditis, during early pregnancy, were found to be associated with several offspring behavioural and psychiatric disorders such as attention deficit hyperactivity disorder (ADHD), autism, pervasive developmental problems, externalising behaviour, in addition to epilepsy and seizure. The majority of associations were found with low maternal thyroid hormone level.

CONCLUSION

Maternal thyroid function during pregnancy, particularly hypothyroidism, is associated with behavioural and psychiatric disorders in children. Further studies are needed with a capacity to adjust for a fuller range of confounding factors.

Thyroid disease in pregnancy: new insights in diagnosis and clinical management

Adequate thyroid hormone availability is important for an uncomplicated pregnancy and optimal fetal growth and development. Overt thyroid disease is associated with a wide range of adverse obstetric and child development outcomes. An increasing number of studies now indicate that milder forms of thyroid dysfunction are also associated with these adverse pregnancy outcomes. The definitions of both overt and subclinical thyroid dysfunction have changed considerably over the past few years, as new data indicate that the commonly used fixed upper limits of 2.5 mU/l or 3.0 mU/l for thyroid-stimulating hormone (TSH) are too low to define an abnormal thyroid function. Furthermore, some studies now show that the reference ranges are not necessarily the best cut-off for identifying pregnancies at high risk of adverse outcomes. In addition, data suggest that thyroid peroxidase autoantibody positivity and high or low concentrations of human chorionic gonadotropin seem to have a more prominent role in the interpretation of thyroid dysfunction than previously thought. Data on the effects of thyroid disease treatment are lacking, but some studies indicate that clinicians should be aware of the potential for overtreatment with levothyroxine. Here, we put studies from the past decade on reference ranges for TSH, determinants of thyroid dysfunction, risks of adverse outcomes and options for treatment into perspective. In addition, we provide an overview of the current views on thyroid physiology during pregnancy and discuss strategies to identify high-risk individuals who might benefit from levothyroxine treatment.

MANAGEMENT OF ENDOCRINE DISEASE: Isolated maternal hypothyroxinemia during pregnancy: knowns and unknowns

Isolated maternal hypothyroxinemia (IMH) during pregnancy is defined as a low maternal T₄ in the absence of TSH elevation. As IMH is common, with a prevalence of 1-2% in iodine-sufficient populations, and early research has suggested adverse effects on fetal neurodevelopment, it has been the focus of many studies in the last decade. In the current review, we first discuss the significance of IMH based on data from animal models and recent discoveries regarding the role of thyroid hormone on neurodevelopment. We address issues surrounding the definition and prevalence of this entity and discuss new insights into the etiologies, clinical consequences and management of IMH. A number of large cohort studies have investigated the effects of IMH on the risk of various pregnancy complications and child neurodevelopment. We review these studies in detail and describe their limitations. We discuss the available research on management of IMH, including two recent randomized controlled trials (RCTs). Finally, we delineate the remaining uncertainties in this field and emphasize the need for a sufficiently powered, placebo-controlled RCT on the treatment of IMH early in the first trimester of pregnancy.

Transient hypothyroxinemia of prematurity and problem behavior in young adulthood

INTRODUCTION

Preterm newborns are at risk of developing transient hypothyroxinemia of prematurity (THoP), which has been associated with subsequent neurodevelopmental impairments. Behavioral outcomes at adult age after THoP have never been reported.

AIM

To examine whether there is an association between THoP and problem behavior at young adult age.

METHODS

This study was part of the follow-up of 19-year-old subjects born very preterm (i.e., <32 weeks) and/or with a very low birth weight (i.e.,<1500g) from the Project On Preterm and Small-for-gestational-age infants (POPS) cohort. We included 468 subjects of the POPS cohort; of whom 123 had THoP. Thyroxine (T4) concentrations were obtained through the national neonatal screening program for congenital hypothyroidism. THoP was defined as a T4 concentration <-3 SD (approximately 60nmol/L). At age 19, behavior was assessed using the Young Adult Self Report and the Young Adult Behavioral Checklist for parents.

RESULTS

THoP was associated with a 1.8 (95% confidence interval (CI): 1.01-3.4) -fold increased odds of self-reported Internalizing behavior, as well as with a 1.9 (95% CI: 1.1-3.1) -fold increased odds of parent-reported Total problem behavior. These relations persisted after correction for demographic and perinatal variables. Similar associations were absent for the other self-reported and parent-reported syndrome and problem scales.

CONCLUSIONS

THoP was associated with more internalizing and total problem behavior at age 19. While our observations warrant more awareness of problem behavior in preterm infants, at present, it is unclear whether these associations are causal and screening for THoP does not seem necessary.

The impact of thyroid abnormalities during pregnancy on subsequent neuropsychological development of the offspring: a meta-analysis

OBJECTIVE

To investigate the relationship between specific thyroid abnormalities in women during pregnancy and the subsequent neuropsychological development of their offspring.

METHODS

A systematic literature search of PubMed, Embase and Web of Science was conducted. Eligible studies were case-control or cohort study that explored this association with euthyroid thyroid abnormalities during pregnancy. The outcomes included intelligence scores and motor scores. Weighted mean differences (WMDs) and 95% confidence intervals (CIs) were calculated and heterogeneity was assessed with Cochrane Q chi-square test and I(2) statistics. A fixed-effects or random-effects model was used to pool the estimates according to the heterogeneity among the included studies.

RESULTS

Six studies, involving 4449 participants, were included. Children of women with thyroid abnormalities had mean intelligence score of 6.27 points and motor score of 5.99 points lower than that of children of euthyroid women. Subgroup analysis suggested that, children of women with hypothyroxinaemia, subclinical hypothyroidism and positive TPOAb had mean intelligence scores of 5.69 points, 8.76 points and 10.55 points, and mean motor scores of 4.19 points, 9.98 points and 9.03 points lower than those of the controls, respectively.

CONCLUSIONS

The thyroid abnormalities in pregnant women may adversely affect neuropsychological development of their offspring.

Effects of Thyroid Peroxidase Antibody on Maternal and Neonatal Outcomes in Pregnant Women in an Iodine-Sufficient Area in China

Purposes. To evaluate the effects of thyroid peroxidase antibodies (TPOAb) on maternal and neonatal adverse outcomes in pregnant women. Methods. 208 pregnant women at 24-28 weeks were divided into two groups, TPOAb-positive and TPOAb-negative groups. Thyroid function and TPOAb were determined in all subjects until 12 months postpartum. Levothyroxine was supplemented to maintain euthyroid with periodical checking of thyroid functions. The prevalence of postpartum thyroiditis (PPT), placenta previa, placental abruption, premature rupture of membrane, postpartum haemorrhage, polyhydramnios, oligohydramnios, preterm birth, low birth weight, congenital hypothyroidism, and neonatal diseases were observed in two groups. Results. Of all women, 11.54% had a PPT. The prevalence of PPT was significantly higher in TPOAb-positive than TPOAb-negative group (42.31% versus 7.14%, P < 0.001), with 45.46% and 53.85% of PPT happening at 6 weeks postpartum in TPOAb-positive and TPOAb-negative groups. The incidence of polyhydramnios was significantly higher in TPOAb-positive than TPOAb-negative group (15.38% versus 2.74%, P = 0.02). Conclusion. Pregnant women with TPOAb-positive had increased risk of PPT, predominantly happening at 6 weeks postpartum. TPOAb was associated with increased incidence of polyhydramnios and the underlying mechanisms required further investigation. Earlier screening of thyroid function during pregnancy and postpartum was warranted in our region.