Effects of iodine deficiency in pregnancy

Vitamins, minerals and their maternal levels' role in brain development: An updated literature-review

One's neurobehavioural and mental health are built during the exact and complex process of brain development. It is thought that fetal development is where neuropsychiatric disorders first emerged. Behavioural patterns can change as a result of neuropsychiatric illnesses. The incidence is rising quickly; nevertheless, providing exceptional care remains a significant challenge for families and healthcare systems. It has been demonstrated that one of the main factors causing the transmission of these diseases is maternal exposure. Through physiologic pathways, maternal health and intrauterine exposures can affect brain development. Our attention has been focused on epigenetic factors, particularly in the gestational environment, which may be responsible for human neurodegenerative diseases since our main mental development occurs during the nine months of intrauterine life. After thoroughly searching numerous databases, this study examined the effect of fat-soluble vitamins, water-soluble vitamins, and minerals and their maternal-level effect on brain development.

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.

Low Iodine Nutrition Knowledge in Chinese Breastfeeding Women despite Adequate Iodine Status

There has been a scarcity of evidence about iodine nutrition knowledge among women during pregnancy and lactation. The aim of this study was to determine women's iodine knowledge and the relationship between knowledge and iodine status during pregnancy and lactation. Women were recruited from a hospital in the western part of China in the third trimester of pregnancy and followed until the end of the first week of lactation. The women's iodine status was measured by their urinary iodine concentration (UIC) and an iodine-specific, validated food frequency questionnaire (FFQ). Iodine nutrition knowledge was assessed using an iodine nutrition knowledge questionnaire. A total of 200 women (mean age of 29.0 ± 4.2 years) completed the whole study. The majority of the women did not consume enough iodine during both pregnancy and lactation (231.89 vs. 237.26 µg/day). The overall mean iodine knowledge scores in our sample of women during pregnancy and lactation were 4.77 and 4.87, indicating low iodine knowledge. The use of iodized salt and a higher education level were significantly associated with an increased iodine knowledge score. In conclusion, this study reported poor iodine nutrition knowledge in women, highlighting a public health concern. Therefore, the iodine knowledge of women should be improved, possibly via maternal health campaigns to avoid the consequences of iodine deficiency disorders in newborns.

Iodine-induced thyroid dysfunction: a scientometric study and visualization analysis

Objective

Iodine is essential in thyroid hormone production. Iodine deficiency is associated with serious complications (i.e miscarriage and stillbirth), whereas excess can cause thyroid dysfunction (i.e hyperthyroidism, hypothyroidism, thyroid autoimmunity). We conducted this scientometric study to visualize hot spots and trends in iodine-induced thyroid dysfunction over past two decades. The aim of this paper was to help scholars quickly understand the development and potential trend in this field, and guide future research directions.

Methods

Articles on iodine-induced thyroid dysfunction from 2000 to 2022 were retrieved from the Web of Science Core Collection (WoSCC) using the following search terms: (((((TS=(hypothyroid*)) OR TS=(hyperthyroid*)) OR TS= ("TSH deficiency")) OR TS= ("thyroid stimulating hormone deficiency")) AND TS=(Iodine)) NOT TS=(radioiodine). Only publications in English were selected. CiteSpace, VOSviewer, Tableau, Carrot2, and R software were used to analyze the contribution and co-occurrence relationships of different countries, institutes, keywords, references, and journals.

Results

A total of 2986 publications from 115 countries and 3412 research institutions were included. From 2000 to 2022, research on iodine-induced thyroid dysfunction progressed over a three-stage development period: initial development (2000-2009), stable development (2010-2016), and rapid development (2016-2022) period. The Journal of Clinical Endocrinology and Metabolism had the most co-citations followed and China Medical University (n=76) had the most publications. The top three clusters of co-citation references were isolated maternal hypothyroxinemia, subclinical hyperthyroidism, and brain development. Various scientific methods were applied to reveal acknowledge structure, development trend and research hotspots in iodine-induced thyroid dysfunction.

Conclusion

Our scientometric analysis shows that investigations related to pregnant women, epidemiology surveys, and iodine deficiency are promising topics for future iodine-induced thyroid dysfunction research and highlights the important role of iodine on thyroid function.

No Association Was Found Between Mild Iodine Deficiency During Pregnancy and Pregnancy Outcomes: a Follow-up Study Based on a Birth Registry

BACKGROUND

Severe iodine deficiency during gestation is associated with adverse pregnancy outcomes; however, the impact of mild-to-moderate iodine deficiency, though prevalent in pregnancy, remains unclear.

METHODS

We extracted follow-up data for 7435 pregnant women from a national iodine deficiency disorders monitoring program from 2016 to 2018 and a mother-child cohort study in 2017 based on a birth registry in Shanghai. Birth outcomes were collected from the registry. Spot urine and household salt samples were collected for iodine testing. Single-factor analysis and logistic regression were used to evaluate the association between maternal iodine status and pregnancy outcomes.

RESULTS

The median urine iodine level in pregnant women was 137.5 μg/L (interquartile range 82.4-211.5), suggesting mild deficiency according to WHO standards. The incidence of pregnancy termination, preterm birth, congenital malformations, low birth weight, and cesarean section was 3.2%, 4.3%, 1.4%, 2.7%, and 45.2% in the mildly iodine-deficient group and 3.4%, 4.5%, 1.4%, 2.7%, and 44.5% in the normal group, respectively. After adjusting for maternal age and education, trimesters, and preterm birth rate in the general population, the odds ratios for any outcome did not differ significantly between the two groups.

CONCLUSION

The present study suggests that mild maternal iodine deficiency is not associated with adverse pregnancy outcomes.

Iodine Status Modifies the Association between Fluoride Exposure in Pregnancy and Preschool Boys' Intelligence

In animal studies, the combination of in utero fluoride exposure and low iodine has greater negative effects on offspring learning and memory than either alone, but this has not been studied in children. We evaluated whether the maternal urinary iodine concentration (MUIC) modifies the association between maternal urinary fluoride (MUF) and boys' and girls' intelligence. We used data from 366 mother-child dyads in the Maternal-Infant Research on Environmental Chemicals Study. We corrected trimester-specific MUF and MUIC for creatinine, and averaged them to yield our exposure variables (MUFCRE, mg/g; MUICCRE, µg/g). We assessed children's full-scale intelligence (FSIQ) at 3 to 4 years. Using multiple linear regression, we estimated a three-way interaction between MUFCRE, MUICCRE, and child sex on FSIQ, controlling for covariates. The MUICCRE by MUFCRE interaction was significant for boys (p = 0.042), but not girls (p = 0.190). For boys whose mothers had low iodine, a 0.5 mg/g increase in MUFCRE was associated with a 4.65-point lower FSIQ score (95% CI: -7.67, -1.62). For boys whose mothers had adequate iodine, a 0.5 mg/g increase in MUFCRE was associated with a 2.95-point lower FSIQ score (95% CI: -4.77, -1.13). These results suggest adequate iodine intake during pregnancy may minimize fluoride's neurotoxicity in boys.

Prevalence of insufficient iodine intake in pregnancy worldwide: a systematic review and meta-analysis

BACKGROUND/OBJECTIVES

Iodine deficiency in pregnant women is related to impaired foetal growth and development. The objective of this study was to estimate the prevalence of insufficient iodine intake in pregnant women from different regions of the world.

SUBJECTS/METHODS

Using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines, five electronic databases and Google Scholar grey literature were searched until 10 April 2021. Two reviewers independently conducted article selection, data extraction, and assessment of the risk of bias. Meta-analyses with random effects, subgroup analyses, and meta-regressions were performed.

RESULTS

In total, 4639 observational articles were found, with 61 eligible for inclusion. The population consisted of 163,021 pregnant women adults and adolescents, and the overall prevalence of insufficient iodine intake was 53% (95% confidence interval [CI]: 47-60; I² = 99.8%). Pregnant women who live in insufficient iodine status country had a higher prevalence (86%; 95% CI: 78-93; I² =97.0%) of inadequate iodine nutritional status than to those living in country considered sufficient (51%; 95% IC: 45-57; I² = 99.8%).

CONCLUSION

Despite the progress in iodine fortification policies and periodic monitoring of the iodine nutritional status of the population worldwide, salt iodination alone may not be sufficient to provide adequate iodine status to pregnant women. Thus, other actions may be necessary to improve the nutritional clinical care of pregnant group.

Assessment and treatment of thyroid disorders in pregnancy and the postpartum period

Thyroid disorders are prevalent in pregnant women. Furthermore, thyroid hormone has a critical role in fetal development and thyroid dysfunction can adversely affect obstetric outcomes. Thus, the appropriate management of hyperthyroidism, most commonly caused by Graves disease, and hypothyroidism, which in iodine sufficient regions is most commonly caused by Hashimoto thyroiditis, in pregnancy is important for the health of both pregnant women and their offspring. Gestational transient thyrotoxicosis can also occur during pregnancy and should be differentiated from Graves disease. Effects of thyroid autoimmunity and subclinical hypothyroidism in pregnancy remain controversial. Iodine deficiency is the leading cause of hypothyroidism worldwide. Despite global efforts to eradicate iodine deficiency disorders, pregnant women remain at risk of iodine deficiency due to increased iodine requirements during gestation. The incidence of thyroid cancer is increasing worldwide, including in young adults. As such, the diagnosis of thyroid nodules or thyroid cancer during pregnancy is becoming more frequent. The evaluation and management of thyroid nodules and thyroid cancer in pregnancy pose a particular challenge. Postpartum thyroiditis can occur up to 1 year after delivery and must be differentiated from other forms of thyroid dysfunction, as treatment differs. This Review provides current evidence and recommendations for the evaluation and management of thyroid disorders in pregnancy and in the postpartum period.

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.

Associations between maternal urinary iodine assessment, dietary iodine intakes and neurodevelopmental outcomes in the child: a systematic review

OBJECTIVE

Mild to moderate iodine deficiency during pregnancy has been associated with adverse neurodevelopmental outcomes in offspring. Few research studies to date combine assessment of urinary iodine (UIC and/or ICr), biomarkers that best reflect dietary intake, with reported dietary intake of iodine rich foods in their assessment of iodine deficiency. Thus, a systematic review was conducted to incorporate both these important measures.

DESIGN

Using PRISMA guidelines, a comprehensive search was conducted in three electronic databases (EMBASE®, MedLine® and Web of Science®) from January 1970-March 2021. Quality assessment was undertaken using the Newcastle Ottawa Scale. Eligible studies included reported assessment of iodine status through urinary iodine (UIC and/or ICr) and/or dietary intake measures in pregnancy alongside neurodevelopmental outcomes measured in the children. Data extracted included study author, design, sample size, country, gestational age, child age at testing, cognitive tests, urinary iodine assessment (UIC in μg/L and/or ICr in μg/g), dietary iodine intake assessment and results of associations for the assessed cognitive outcomes.

RESULTS

Twelve studies were included with nine reporting women as mild-moderately iodine deficient based on World Health Organization (WHO) cut-offs for urinary iodine measurements < 150 μg/l, as the median UIC value in pregnant women. Only four of the nine studies reported a negative association with child cognitive outcomes based on deficient urinary iodine measurements. Five studies reported urinary iodine measurements and dietary intakes with four of these studies reporting a negative association of lower urinary iodine measurements and dietary iodine intakes with adverse offspring neurodevelopment. Milk was identified as the main dietary source of iodine in these studies.

CONCLUSION

The majority of studies classified pregnant women to be mild-moderately iodine deficient based on urinary iodine assessment (UIC and/or ICr) and/or dietary intakes, with subsequent offspring neurodevelopment implications identified. Although a considerable number of studies did not report an adverse association with neurodevelopmental outcomes, these findings are still supportive of ensuring adequate dietary iodine intakes and urinary iodine monitoring throughout pregnancy due to the important role iodine plays within foetal neurodevelopment. This review suggests that dietary intake data may indicate a stronger association with cognitive outcomes than urinary iodine measurements alone. The strength of this review distinguishes results based on cognitive outcome per urinary iodine assessment strategy (UIC and/or ICr) with dietary data. Future work is needed respecting the usefulness of urinary iodine assessment (UIC and/or ICr) as an indicator of deficiency whilst also taking account of dietary intakes.

Iron, iodine and vitamin D deficiencies during pregnancy: epidemiology, risk factors and developmental impacts

Micronutrient deficiency persists throughout the world, and although the burden is higher in low-resource settings, it is also prevalent in wealthy countries, a phenomenon termed 'hidden hunger'. Due to their high requirements for vitamins and minerals relative to their energy intake, young women and children are particularly vulnerable to hidden hunger. As they share several risk factors and impact on overlapping outcomes, we consider how deficiency of iron, iodine and vitamin D can have profound impacts on perinatal health and infant development. We review the epidemiology of these micronutrient deficiencies during pregnancy, including social, environmental and dietary risk factors. We identify the main challenges in defining nutritional status of these nutrients using validated diagnostic criteria linked with meaningful clinical outcomes. Public health strategies are urgently required to improve the overall health and nutritional status of women of reproductive age. Obesity prevention and early detection of malnutrition with standardised screening methods would detect pregnant women at increased risk of iron deficiency. Development of sensitive, individual biomarkers of iodine status is required to protect maternal health and fetal/infant brain development. Risk assessments of vitamin D requirements during pregnancy need to be revisited from the perspective of fetal and neonatal requirements. International consensus on standardised approaches to micronutrient assessment, analysis and reporting as well as sensitive, clinically validated infant and child neuro-behavioural outcomes will enable progression of useful observational and intervention studies.

Case Report: Functional Analysis and Neuropsychological Evaluation of Dyshormonogenetic Fetal Goiter in Siblings Caused by Novel Compound Hyterozygous TPO Gene Mutations

INTRODUCTION

It is rare for a euthyroid mother to carry a child with a fetal goiter. However, cases of congenital hypothyroidism (CH) caused by thyroid dyshormonogenesis have been reported. Even though gene mutations associated with fetal goiter have been reported in a few studies, the effects on intellectual development have not been investigated. This study aimed to characterize and investigate the underlying genetic mechanism of CH and neuropsychological development and growth of two siblings with CH-induced fetal goiters.

CASE REPORT

Two male siblings from a non-consanguineous marriage with CH and fetal goiter were diagnosed by ultrasonography at 32- and 26-weeks of gestation. This condition was confirmed by cordocentesis in the first pregnancy (TSH: 135 μIU/ml). The mother was euthyroid, and no intra-amniotic levothyroxine treatment was performed. Peripheral blood DNA was screened for TPO mutations. The new deletion p.Cys296Alafs*21 and the p.Arg665Trp mutation, inherited from heterozygous parents, were identified in both patients. Functional analysis showed both mutations reduced the TPO enzyme activity and impaired the membrane localization. The p.Cys296Alafs*21 mutation produces a protein product with a drastically reduced molecular weight. Additionally, a complete clinical and neuropsychological evaluation was also performed. The WISC IV test was employed to provide an overall measure of the siblings' cognitive and intellectual abilities. No growth retardation was detected in either child. In general, both children showed normal neuropsychological development; however, they exhibited slight reduction of Processing Speed Index scores, which are sensitive to neurological and attentional factors and motor maturation activity. Notably, the younger sibling obtained significantly low scores in the Operational Memory Index, a measure of attention capacity and psychoneurological immaturity.

CONCLUSION

We described a new TPO compound heterozygosity that severely impaired the TPO activity and membrane localization leading to severe CH and fetal goiter. This is the first report showing the neuropsychological evaluation in patients with dyshormonogenetic fetal goiter. More studies are needed to understand the neurodevelopmental outcomes of neonates with CH-induced fetal goiters.

Maternal Urinary Iodine Concentration and Pregnancy Outcomes: Tehran Thyroid and Pregnancy Study

Iodine is essential for the production of thyroid hormones, and its deficiency during pregnancy may be associated with poor obstetric outcomes. The aim of this study was to investigate the relationship between maternal iodine statuses with pregnancy outcomes among pregnant Iranian women, considering their baseline thyrotropin (TSH) status. We used data from the Tehran Thyroid and Pregnancy Study (TTPS), a two-phase population-based study carried out among pregnant women receiving prenatal care. By excluding participants with overt thyroid dysfunction and those receiving levothyroxine, the remaining participants (n = 1286) were categorized into four groups, according to their urine iodine status: group 1, urine iodine concentration (UIC) < 100 μg/L; group 2, UIC between 100 and 150 μg/L; group 3, UIC between 150 and 250 μg/L; and group 4, UIC ≥ 250 μg/L. Primary outcome was preterm delivery. Preterm delivery occurred in 29 (9%), 19 (7%), 15 (5%), and 8 (4%) women, and neonatal admission was documented in 22 (7%), 30 (12%), 28 (11%), and 6 (3%) women of groups 1, 2, 3, and 4, respectively. Generalized linear regression model (GLM) demonstrated that the odds ratio of preterm delivery was significantly higher in women with urinary iodine < 100 μg/L and TSH ≥ 4 μIU/mL than those with similar urinary iodine with TSH < 4 μIU/mL (OR 2.5 [95% CI 1.1, 10], p = 0.024). Adverse pregnancy outcomes are increased among women with UIC < 100 μg/L, with serum TSH concentrations ≥ 4 μIU/mL.

Maternal Iodine Insufficiency and Excess Are Associated with Adverse Effects on Fetal Growth: A Prospective Cohort Study in Wuhan, China

Background

Maternal iodine status has been suggested to affect birth outcomes. Few studies have focused on its effects on fetal growth during pregnancy.

Objective

This study aimed to assess maternal iodine status during early pregnancy and further examine the relation between maternal iodine status and fetal growth.

Methods

A total of 2087 singleton-pregnant women participating in the Tongji Maternal and Child Health Cohort study were involved. Urinary iodine concentration (UIC) and creatinine concentration were measured in spot urine samples collected in early pregnancy (<20 wk of gestation). Fetal head circumference (HC), femur length (FL), and estimated fetal weight (EFW) were evaluated by ultrasonography in each trimester. A multiple linear regression model was used to examine the association of iodine status with fetal growth characteristics, and a mixed-effects model was used to assess longitudinal effect.

Results

The median UIC and iodine-to-creatinine (I/Cr) ratio were 178 μg/L and 234 μg/g, respectively. The prevalence of insufficient iodine status (I/Cr ratio <150 μg/g) was 19.8%(n = 414), of adequate iodine status (150-249 μg/g) was 34.8% (n = 726), of iodine status above the requirements (250-499 μg/g) was 32.1% (n = 669), and of excessive iodine status (≥500 μg/g) was 13.3% (n = 278). Maternal iodine insufficiency was inversely associated with fetal FL in the second and third trimesters. In stratified analysis, significant interactions were found between maternal iodine status and age as well as parity (all P < 0.05). The longitudinal analyses showed negative associations of maternal insufficient, more than adequate, or excessive iodine status with fetal growth during pregnancy (all P < 0.05).

Conclusions

In central China, maternal iodine insufficiency and excess coexisted during early pregnancy and they both adversely affected fetal growth. There is an urgent need for ongoing monitoring of iodine status among vulnerable pregnant women in order to optimize iodine nutrition during pregnancy.

Nitric oxide is involved in the hypothyroidism with significant morphology changes in female Wistar rats induced by chronic exposure to high water iodine from potassium iodate

Epidemiological studies indicated that chronic exposure to high water iodine is associated with primary hypothyroidism (PH) and subclinical hypothyroidism (SCH). However, the mechanism is not well understood. In this study, we explored whether chronic exposure to high water iodine from potassium iodate (KIO₃) can induce hypothyroidism in addition to determining if nitric oxide (NO) is involved in the pathogenesis. 96 female Wistar rats were divided into six groups: control, I_1000μg/L, I_3000μg/L, I_6000μg/L, N-nitro-L-arginine methylester (L-NAME) and L-NAME+I_6000μg/L. After 3 months, urine iodine concentration, thyroid hormone, NO and nitric oxide synthase (NOS) serum levels were determined. Additionally, thyroid expression of inducible nitric oxide synthase (iNOS) was also investigated. Thyroid morphology was observed under light microscopy and transmission electron microscope. SCH as indicated by elevated serum thyrotropin (TSH) was induced among rats exposed to 3000 μg/L I^-, while rats treated with 6000 μg/L I^- presented PH characterized by elevated TSH and lowered total thyroxine in serum. Moreover, serum NO, NOS and iNOS expression in the thyroid were significantly increased in I_3000μg/L and I_6000μg/L groups. Changes in thyroid function and morphology in the L-NAME+I_6000μg/L group were extenuated compared to I_6000μg/L group. These findings suggested that chronic exposure to high water iodine from KIO₃ likely induces hypothyroidism with significant morphology changes in female Wistar rats and NO appears to be involved in the pathogenesis.

Associations of maternal iodine status and thyroid function with adverse pregnancy outcomes in Henan Province of China

OBJECTIVE

The study aimed to explore the effects of maternal iodine status and thyroid diseases on adverse pregnancy outcomes.

METHODS

A prospective study was conducted on 2347 pregnant women, who provided 2347 urinary samples tested for iodine, 1082 serum samples tested for thyroid function, and 2347 questionnaires about demographic information. Their pregnancy outcomes were recorded and compared between different urinary iodine concentration (UIC) and thyroid function groups.

RESULTS

Pregnant women with UIC between 150 and 249 μg/L had lower incidences of preeclampsia (adjusted odds ratio (OR) 0.12, 95% CI: 0.01-0.87), placenta previa (adjusted OR 0.06, 95% CI: 0.01-0.69) and fetal distress (adjusted OR 0.10, 95% CI: 0.02-0.64) than the reference group (UIC < 50 μg/L). Women with UIC between 100 and 149 μg/L had lower risks of abnormal amniotic fluid (adjusted OR 0.32, 95% CI: 0.12-0.87) and fetal distress (adjusted OR 0.08, 95% CI: 0.01-0.82). Women with UIC above 249 μg/L had a significant higher rate of abnormal amniotic fluid (adjusted OR 0.38, 95% CI: 0.16-0.89). Clinical and subclinical hypothyroidism during pregnancy increased the risk of preterm delivery by 4.4 times (P = 0.009) and 3.0 times (P =  0.014), respectively. Isolated hypothyroxinemia had increased odds of having macrosomia (adjusted OR 2.22, 95% CI: 1.13-4.85). Clinical hyperthyroidism was significantly associated with miscarriage (adjusted OR 2.12, 95% CI: 1.92-96.67) and fetal distress (adjusted OR 9.53, 95% CI: 1.05--81.81). Subclinical hyperthyroidism had a significant association with umbilical cord entanglement (adjusted OR 3.82, 95% CI: 1.38-10.58). Isolated hyperthyroxinemia was associated with preterm delivery (adjusted OR 4.73, 95% CI: 1.49-15.05).

CONCLUSIONS

Maternal iodine status and thyroid diseases during pregnancy were associated with adverse pregnancy outcomes.

Suboptimal Iodine Status among Pregnant Women in the Oslo Area, Norway

Norway has been considered iodine replete for decades; however, recent studies indicate reemergence of inadequate iodine status in different population groups. We assessed iodine status in pregnant women based on urinary iodine concentration (UIC), urinary iodine excretion (UIE), and iodine intake from food and supplements. In 804 pregnant women, 24-h iodine intakes from iodine-rich foods and iodine-containing supplements were calculated. In 777 women, iodine concentration was measured in spot urine samples by inductively coupled plasma/mass spectrometry (ICP-MS). In addition, 49 of the women collected a 24-h urine sample for assessment of UIE and iodine intake from food frequency questionnaire (FFQ). Median UIC was 92 µg/L. Fifty-five percent had a calculated iodine intake below estimated average requirement (EAR) (160 µg/day). Iodine intake from food alone did not provide the amount of iodine required to meet maternal and fetal needs during pregnancy. In multiple regression models, hypothyroidism, supplemental iodine and maternal age were positively associated with UIC, while gestational age and smoking were negatively associated, explaining 11% of the variance. This study clearly shows that pregnant women in the Oslo area are mild to moderate iodine deficient and public health strategies are needed to improve and secure adequate iodine status.

Effect of the micronutrient iodine in thyroid carcinoma angiogenesis

Iodide is a micronutrient essential for thyroid hormone production. The uptake and metabolism of iodide by thyrocytes is crucial to proper thyroid function. Iodide ions are drawn into the thyroid follicular cell via the sodium-iodide symporter (NIS) in the cell membrane and become integrated into tyrosyl residues to ultimately form thyroid hormones. We sought to learn how an abnormal concentration of iodide within thyrocyte can have significant effects on the thyroid, specifically the surrounding vascular network. Insufficient levels of iodide can lead to increased expression or activity of several pathways, including vascular endothelial growth factor (VEGF). The VEGF protein fuel vessel growth (angiogenesis) and therefore enhances the nutrients available to surrounding cells. Alternatively, normal/surplus iodide levels can have inhibitory effects on angiogenesis. Varying levels of iodide in the thyroid can influence thyroid carcinoma cell proliferation and angiogenesis via regulation of the hypoxia inducible factor-1 (HIF-1) and VEGF-dependent pathway. We have reviewed a number of studies to investigate how the effect of iodide on angiogenic and oxidative stress regulation can affect the viability of thyroid carcinoma cells. The various studies outlined give key insights to the role of iodide in thyroid follicles function and vascular growth, generally highlighting that insufficient levels of iodide stimulate pathways resulting in vascular growth, and viceversa normal/surplus iodide levels inhibit such pathways. Intriguingly, TSH and iodine levels differentially regulate the expression levels of angiogenic factors. All cells, including carcinoma cells, increase uptake of blood nutrients, meaning the vascular profile is influential to tumor growth and progression. Importantly, variation in the iodine concentrations also influence BRAF^V600E-mediated oncogenic activity and might deregulate tumor proliferation. Although the mechanisms are not well eluted, iodine concentrations and metabolism might have a crucial influence on thyroid carcinoma cell viability via regulation of different molecular pathways, including angiogenesis regulatory autocrine and microenvironment-mediated signals.

Thyroid antagonists and thyroid indicators in U.S. pregnant women in the Vanguard Study of the National Children's Study

The sodium iodide-symporter (NIS) mediates uptake of iodide into thyroid follicular cells. This key step in thyroid hormone synthesis is inhibited by perchlorate, thiocyanate (SCN) and nitrate (NO3) anions. When these exposures occur during pregnancy the resulting decreases in thyroid hormones may adversely affect neurodevelopment of the human fetus. Our objectives were to describe and examine the relationship of these anions to the serum thyroid indicators, thyroid stimulating hormone (TSH) and free thyroxine (FT4), in third trimester women from the initial Vanguard Study of the National Children's Study (NCS); and to compare urine perchlorate results with those in pregnant women from the National Health and Nutritional Examination Survey (NHANES). Urinary perchlorate, SCN, NO3, and iodine, serum TSH, FT4, and cotinine were measured and a food frequency questionnaire (FFQ) was administered to pregnant women enrolled in the initial Vanguard Study. We used multiple regression models of FT4 and TSH that included perchlorate equivalent concentration (PEC, which estimates combined inhibitory effects of the anions perchlorate, SCN, and NO3 on the NIS). We used multiple regression to model predictors of each urinary anion, using FFQ results, drinking water source, season of year, smoking status, and demographic characteristics. Descriptive statistics were calculated for pregnant women in NHANES 2001-2012. The geometric mean (GM) for urinary perchlorate was 4.04µg/L, for TSH 1.46mIU/L, and the arithmetic mean for FT4 1.11ng/dL in 359 NCS women. In 330 women with completed FFQs, consumption of leafy greens, winter season, and Hispanic ethnicity were significant predictors of higher urinary perchlorate, which differed significantly by study site and primary drinking water source, and bottled water was associated with higher urinary perchlorate compared to filtered tap water. Leafy greens consumption was associated with higher urinary NO3 and higher urinary SCN. There was no association between urinary perchlorate or PEC and TSH or FT4, even for women with urinary iodine <100µg/L. GM urinary perchlorate concentrations in the full sample (n=494) of third trimester NCS women (4.03µg/L) were similar to pregnant women in NHANES (3.58µg/L).

Evaluation of iodine intake and status using inductively coupled plasma mass spectrometry in urban and rural areas in Benin, West Africa

OBJECTIVE

Iodine deficiency has severe pathological repercussions. The aim of this study was to evaluate iodine intake and status in adults in Benin, West Africa.

METHODS

We randomly selected 420 participants ages 25 to 64 y and free of visible goiter from urban and rural settings of South Benin. The participants had a diet based on carbohydrates and fish. Urine was collected over a 24-h period and samples were assayed for iodine analysis using inductively coupled plasma mass spectrometry.

RESULTS

We studied 401 urinary iodine samples. The overall median urinary iodine concentration (UIC) in 24-h urine was 62.9 μg/L (interquartile range: 40-96.2 μg/L). UIC was significantly lower in women than men (56.5 versus 78.6 μg/L; P < 0.001) and in rural versus urban areas (54.7 versus 77.8 μg/L; P < 0.001). In multivariate analysis, low UIC (<100 μg/L) was positively associated with women (odds ratio, 2.48; 95% confidence interval, 1.44-4.26; P = 0.001) and body mass index <25 kg/m(2) (odds ratio, 2.06; 95% confidence interval, 1.20-3.54; P = 0.008).

CONCLUSION

Iodine intake appeared to be fairly low in the Beninese population, according to World Health Organization criteria, and factors associated with low iodine intake were identified. Public health interventions to increase iodine intake, such as iodization of commercial salt and/or fortification of selected nutrients, should be strengthened at the national level.

Maternal iodine insufficiency and adverse pregnancy outcomes

This study aimed to assess the iodine status of pregnant women in each trimester and to compare the pregnancy outcomes between groups with iodine insufficiency and iodine sufficiency. Longitudinal study on urinary iodine concentration (UIC) in each trimester as well as comparison between women with iodine insufficiency (<150 mcg L(-1) ) and iodine sufficiency was conducted. Pregnant women without thyroid diseases who had not received iodine supplementation were recruited for UIC measurements in each trimester and were followed up for pregnancy outcomes. In the analysis of 384, 325 and 221 samples in the first, second and third trimester, the medians of UICs were 147.39, 157.01 and 153.07 mcg L(-1) , respectively. Of 399 women, 174 (43.6%) had a UIC less than 150 mcg L(-1) (suggesting iodine insufficiency) and 225 (56.4%) had a UIC greater than or equal to 150 mcg L(-1) (suggesting iodine sufficiency). Of 390 women with availability of the final outcomes, 171 and 219 in the insufficiency and sufficiency group, respectively, the rates of preterm birth and low birthweight were significantly higher in the insufficiency group, 17.5% vs. 10.0% (P = 0.031) and 19.9% vs. 12.3% (P = 0.042), respectively. Logistic regression analysis showed that iodine status was an independent risk of preterm birth and low birthweight. Finally, women with a UIC <100 mcg L(-1) had a significantly higher rate of fetal growth restriction, 13/68 vs. 30/322 (P = 0.031). In northern Thailand, a great number of pregnant women had a median UIC less than 150 mcg L(-1) and they had a higher risk of preterm birth and low birthweight. Finally, those with a median UIC of less than 100 mcg L(-1) had a higher risk of fetal growth restriction.

Costs and benefits of iodine supplementation for pregnant women in a mildly to moderately iodine-deficient population: a modelling analysis

BACKGROUND

Results from previous studies show that the cognitive ability of offspring might be irreversibly damaged as a result of their mother's mild iodine deficiency during pregnancy. A reduced intelligence quotient (IQ) score has broad economic and societal cost implications because intelligence affects wellbeing, income, and education outcomes. Although pregnancy and lactation lead to increased iodine needs, no UK recommendations for iodine supplementation have been issued to pregnant women. We aimed to investigate the cost-effectiveness of iodine supplementation versus no supplementation for pregnant women in a mildly to moderately iodine-deficient population for which a population-based iodine supplementation programme--for example, universal salt iodisation--did not exist.

METHODS

We systematically searched MEDLINE, Embase, EconLit, and NHS EED for economic studies that linked IQ and income published in all languages until Aug 21, 2014. We took clinical data relating to iodine deficiency in pregnant women and the effect on IQ in their children aged 8-9 years from primary research. A decision tree was developed to compare the treatment strategies of iodine supplementation in tablet form with no iodine supplementation for pregnant women in the UK. Analyses were done from a health service perspective (analysis 1; taking direct health service costs into account) and societal perspective (analysis 2; taking education costs and the value of an IQ point itself into account), and presented in terms of cost (in sterling, relevant to 2013) per IQ point gained in the offspring. We made data-supported assumptions to complete these analyses, but used a conservative approach that limited the benefits of iodine supplementation and overestimated its potential harms.

FINDINGS

Our systematic search identified 1361 published articles, of which eight were assessed to calculate the monetary value of an IQ point. A discounted lifetime value of an additional IQ point based on earnings was estimated to be £3297 (study estimates range from £1319 to £11,967) for the offspring cohort. Iodine supplementation was cost saving from both a health service perspective (saving £199 per pregnant woman [sensitivity analysis range -£42 to £229]) and societal perspective (saving £4476 per pregnant woman [sensitivity analysis range £540 to £4495]), with a net gain of 1·22 IQ points in each analysis. Base case results were robust to sensitivity analyses.

INTERPRETATION

Iodine supplementation for pregnant women in the UK is potentially cost saving. This finding also has implications for the 1·88 billion people in the 32 countries with iodine deficiency worldwide. Valuation of IQ points should consider non-earnings benefits--eg, health benefits associated with a higher IQ not germane to earnings.

FUNDING

None.

Maternal Hypothyroxinemia-Induced Neurodevelopmental Impairments in the Progeny

Maternal hypothyroxinemia can induce neurodevelopmental impairments in the developing fetus. We here review recent studies on the epidemiology and molecular mechanisms associated with this important public health issue. In 2011, the American Thyroid Association defined maternal hypothyroxinemia as low serum free thyroxine (FT4) levels (<5th or <10th percentile) existing in conjunction with normal serum free triiodothyronine (FT3) or thyroid stimulating hormone (TSH) levels during pregnancy. Compared to clinical or subclinical hypothyroidism, hypothyroxinemia is more commonly found in pregnant women. Hypothyroxinemia usually ensues in response to several factors, such as mild iodine deficiency, environmental endocrine disrupters, or certain thyroid diseases. Unequivocal evidence demonstrates that maternal hypothyroxinemia leads to negative effects on fetal brain development, increasing the risks for cognitive deficits and poor psychomotor development in resulting progeny. In support of this, rodent models provide direct evidence of neurodevelopmental damage induced by maternal hypothyroxinemia, including dendritic and axonal growth limitation, neural abnormal location, and synaptic function alteration. The neurodevelopmental impairments induced by hypothyroxinemia suggest an independent role of T4. Increasing evidence indicates that adequate thyroxine is required for the mothers in order to protect against the abnormal brain development in their progeny.

Iodine status from childhood to adulthood in females living in North-East Italy: Iodine deficiency is still an issue

PURPOSE

This survey aimed to assess iodine status in a female population at different ages, also investigating their eating habits.

METHODS

We measured urinary iodine concentrations (UIC) in: 634 females at puberty and 361 fertile women in 246 of whom were considered also their children (134 daughters and 120 sons). All subjects completed a food frequency questionnaire.

RESULTS

Median UIC decreased from childhood to adulthood (median UIC 107, 77 and 55 μg/l in the young girls, females at puberty and fertile women, respectively). Though using iodized salt improved iodine status in all groups, a significantly higher UIC was only noted in females at puberty. Milk consumption significantly increased UIC at all ages. In mother-child (both daughters and sons) pairs, the children's median UIC was nearly twice as high as their mothers' (UIC 115 vs. 57 μg/l). Milk consumption varied significantly: 56% of the mothers and 76% of their children drank milk regularly. The children (both daughters and sons) and mothers who drank milk had UIC ≥100 μg/l in 59 and 34% of cases, respectively, among the pairs who did not drink milk, 44% of the children and 19% of the mothers had UIC ≥100 μg/l. On statistical regression, 3.6% of the variability in the children's UIC depended on that of their mothers.

CONCLUSIONS

Dietary iodine status declines from childhood to adulthood in females due to different eating habits. A mild iodine deficiency emerged in women of child-bearing age that could have consequences during pregnancy and lactation.

Iodine deficiency and excess coexist in china and induce thyroid dysfunction and disease: a cross-sectional study

Background

In spite of the salt iodization, iodine deficiency disorders (IDD) have not been sustainably eliminated in China. There are coastal areas with low iodized salt coverage rates (iodine nutrition is inadequate) and other areas with excessive amounts of iodine in the drinking water.

Objective

This study aimed to clarify the association of iodine deficiencies resulting from a low coverage rate of iodized salt, excess iodine intake from drinking water with thyroid function and disease in adults.

Design

A cross-sectional study was conducted in adults in different iodine nutrition areas in three provinces in China.

Results

The prevalence of thyroid nodules was 15.52%, 8.66% and 22.17% in the iodine excess, sufficient and deficient groups, respectively. The prevalence of subclinical hypothyroidism was 20.09%, 10.41%, and 2.25% in the excess, sufficient and deficient iodine groups, respectively. The prevalence of subclinical hyperthyroidism and overt hyperthyroidism in the iodine deficient group was higher than that in the iodine excess group ( = 9.302, p = 0.002) and iodine sufficient group ( = 7.553, p = 0.006). Thyroid-stimulating hormone (TSH) was significantly correlated with excess iodine intake (β = 1.764,P = 0.001) and deficient iodine intake (β = −1.219, P = 0.028).

Conclusions

Thyroid nodules are more likely to be present in the iodine excess and deficient areas than in the iodine sufficient areas. Subclinical hyperthyroidism and overt hyperthyroidism are more likely to be prevalent in the iodine deficient areas than in the iodine excess or sufficient areas. Subclinical hypothyroidism is more likely to be prevalent in the high iodine intake areas than in the iodine deficient or sufficient areas. Median TSH may be deemed as an alternative indicator for monitoring the iodine nutrition status of the adult population in iodine excess and deficient areas.

Maternal urinary iodine concentration up to 1.0 mg/L is positively associated with birth weight, length, and head circumference of male offspring

Adequate iodine status in early life is crucial for neurodevelopment. However, little is known about the effects of maternal iodine status during pregnancy on fetal growth. The present study investigated the potential impact of maternal iodine status during pregnancy on offspring birth size. This large prospective cohort study was nested in a Bangladeshi population-based randomized supplementation trial in pregnant women [MINIMat (Maternal and Infant Nutrition Interventions in Matlab)]. Urine samples obtained at 8 wk of gestation from 1617 women were analyzed for iodine and other elements, such as arsenic and cadmium, using inductively coupled plasma mass spectrometry. Anthropometric measurements at birth included weight, length, and head and chest circumference. Maternal urinary iodine concentrations (UICs) ranged from 0.020 to 10 mg/L, with a median of 0.30 mg/L. Below ∼1.0 mg/L, UIC was significantly positively associated with birth weight and length. Birth weight and length increased by 9.3 g (95% CI: 2.9, 16) and 0.042 cm (95% CI: 0.0066, 0.076), respectively, for each 0.1-mg/L increase in maternal UIC. No associations were observed between UIC and head or chest circumference. When we stratified the analyses by newborn sex, the positive associations between maternal UIC (<1 mg/L) and measurements of size at birth were restricted to boys, with no evidence in girls. Among boys, the mean weight, length, and head circumference increased by 70 g (P = 0.019), 0.41 cm (P = 0.013), and 0.28 cm (P = 0.031) for every 0.5-mg/L increase in maternal UIC. Maternal iodine status was positively associated with weight, length, and head circumference in boys up to ∼1 mg/L, which is well above the recommended maximum concentration of 0.5 mg/L. The associations leveled off at UIC ≥ 1 mg/L. Our findings support previous conclusions that the advantages of correcting potential iodine deficiency outweigh the risks of excess exposure.

Urgent global opportunities to prevent birth defects

Birth defects are an urgent global health priority. They affect millions of births worldwide. But their prevalence and impact are largely under-ascertained, particularly in middle- and low-income countries. Fortunately, a large proportion of birth defects can be prevented. This review examines the global prevalence and primary prevention methods for major preventable birth defects: congenital rubella syndrome, folic acid-preventable spina bifida and anencephaly, fetal alcohol syndrome, Down syndrome, rhesus hemolytic disease of the fetus and the newborn; and those associated with maternal diabetes, and maternal exposure to valproic acid or iodine deficiency during pregnancy. Challenges to prevention efforts are reviewed. The aim of this review is to bring to the forefront the urgency of birth defects prevention, surveillance, and prenatal screening and counseling; and to help public health practitioners develop population-based birth defects surveillance and prevention programs, and policy-makers to develop and implement science-based public health policies.

Women with high early pregnancy urinary iodine levels have an increased risk of hyperthyroid newborns: the population-based Generation R Study

OBJECTIVE

Iodine deficiency during pregnancy results in thyroid dysfunction and has been associated with adverse obstetric and foetal effects, leading to worldwide salt iodization programmes. As nowadays 69% of the world's population lives in iodine-sufficient regions, we investigated the effects of variation in iodine status on maternal and foetal thyroid (dys)function in an iodine-sufficient population.

DESIGN, PARTICIPANTS AND MEASUREMENTS

Urinary iodine, serum TSH, free T4 (FT4) and TPO-antibody levels were determined in early pregnancy (13·3 (1·9) week; mean (SD)) in 1098 women from the population-based Generation R Study. Newborn cord serum TSH and FT4 levels were determined at birth.

RESULTS

The median urinary iodine level was 222·5 μg/l, indicating an iodine-sufficient population. 30·8% and 11·5% had urinary iodine levels <150 and >500 μg/l, respectively. When comparing mothers with urinary iodine levels <150 vs ≥150 μg/l, and >500 vs ≤500 μg/l, there were no differences in the risk of maternal increased or decreased TSH, hypothyroxinaemia or hyperthyroidism. Mothers with urinary iodine levels >500 μg/l had a higher risk of a newborn with decreased cord TSH levels (5·6 ± 1·4 (mean ± SE) vs 2·1 ± 0·5%, P = 0·04), as well as a higher risk of a hyperthyroid newborn (3·1 ± 0·9 vs 0·6 ± 0·3%, P = 0·02). These mothers had newborns with higher cord FT4 levels (21·7 ± 0·3 vs 21·0 ± 0·1 pm, P = 0·04). Maternal urinary iodine levels <150 μg/l were not associated with newborn thyroid dysfunction.

CONCLUSIONS

In an iodine-sufficient population, higher maternal urinary iodine levels are associated with an increased risk of a hyperthyroid newborn.

Iodine supplementation in the newborn

Iodine deficiency can be defined as the world's greatest single cause of preventable brain damage. Fetal and neonatal hypothyroidism, caused by iodine deficiency can be prevented prior to conception and then during pregnancy and lactation when an adequate iodine supplementation is ensured. Extremely low birth weight preterm babies risk having a negative iodine balance status in the first weeks of life, exacerbating the hypothyroxinaemia of the prematurity. It is important to ensure that these babies are provided with an adequate iodine intake from the first days of life. Mothers and newborns should avoid environmental iodine excess during pregnancy or lactation.

Gestational hypothyroidism increases the severity of experimental autoimmune encephalomyelitis in adult offspring

BACKGROUND

Maternal thyroid hormones play a fundamental role in appropriate fetal development during gestation. Offspring that have been gestated under maternal hypothyroidism suffer cognitive impairment. Thyroid hormone deficiency during gestation can significantly impact the central nervous system by altering the migration, differentiation, and function of neurons, oligodendrocytes, and astrocytes. Given that gestational hypothyroidism alters the immune cell ratio in offspring, it is possible that this condition could result in higher sensitivity for the development of autoimmune diseases.

METHODS

Adult mice gestated under hypothyroidism were induced with experimental autoimmune encephalomyelitis (EAE). Twenty-one days after EAE induction, the disease score, myelin content, immune cell infiltration, and oligodendrocyte death were evaluated.

RESULTS

We observed that mice gestated under hypothyroidism showed higher EAE scores after disease induction during adulthood compared to mice gestated in euthyroidism. In addition, spinal cord sections of mice gestated under hypothyroidism that suffered EAE in adulthood showed higher demyelination, CD4(+) and CD8(+) infiltration, and increased oligodendrocyte death.

CONCLUSIONS

These results show for the first time that a deficiency in maternal thyroid hormones during gestation can influence the outcome of a central nervous system inflammatory disease, such as EAE, in their offspring. These data strongly support evaluating thyroid hormones in pregnant women and treating hypothyroidism during pregnancy to prevent increased susceptibility to inflammatory diseases in the central nervous system of offspring.