Maternal thyroid dysfunction and risk of seizure in the child: a Danish nationwide cohort study

Levothyroxine Treatment Among Pregnant Women and Risk of Seizure in Children: A Population-Based Cohort Study

INTRODUCTION AND OBJECTIVE

The risk of seizure in offspring following prenatal exposure to levothyroxine is not well investigated. This study aimed to evaluate the association between levothyroxine treatment among pregnant women and the risk of seizure in their offspring.

METHODS

This population-based cohort study included all pregnant women who delivered a live birth between January 2001 to January 2018, with a follow-up to December 2020, using data from the Hong Kong Clinical Data Analysis and Reporting System. Propensity score fine-stratification weighted hazard ratios (wHR) with 95% confidence intervals (CIs) were presented to assess the association between maternal levothyroxine use during pregnancy and seizures in children.

RESULTS

Among 528,343 included mother-child pairs, 3044 children were prenatally exposed to levothyroxine at any time during the pregnancy period. A significantly increased risk of seizure was observed in children of the prenatally exposed group compared with the prenatally unexposed group (wHR 1.12, 95% CI 1.02-1.22). An increased risk of seizure was observed when comparing the prenatally exposed group with euthyroid mothers who had no history of thyroid-related diagnosis or prescriptions (wHR 1.12, 95% CI 1.02-1.23). However, no significant difference was observed between the prenatally exposed group and those previously exposed to levothyroxine but had stopped during pregnancy (wHR 0.97, 95% CI 0.66-1.44). No significant difference was observed in the sibling-matched analysis either (wHR 1.23, 95% CI 0.76-2.01).

CONCLUSION

The observed increased risk of seizure in children born from mothers exposed to levothyroxine during pregnancy might be due to residual confounding by maternal thyroid disease. The findings support the current guidelines on the safe use of levothyroxine treatment during pregnancy.

Thyroid hormone action during GABAergic neuron maturation: The quest for mechanisms

Thyroid hormone (TH) signaling plays a major role in mammalian brain development. Data obtained in the past years in animal models have pinpointed GABAergic neurons as a major target of TH signaling during development, which opens up new perspectives to further investigate the mechanisms by which TH affects brain development. The aim of the present review is to gather the available information about the involvement of TH in the maturation of GABAergic neurons. After giving an overview of the kinds of neurological disorders that may arise from disruption of TH signaling during brain development in humans, we will take a historical perspective to show how rodent models of hypothyroidism have gradually pointed to GABAergic neurons as a main target of TH signaling during brain development. The third part of this review underscores the challenges that are encountered when conducting gene expression studies to investigate the molecular mechanisms that are at play downstream of TH receptors during brain development. Unravelling the mechanisms of action of TH in the developing brain should help make progress in the prevention and treatment of several neurological disorders, including autism and epilepsy.

Local Thyroid Hormone Action in Brain Development

Proper brain development essentially depends on the timed availability of sufficient amounts of thyroid hormone (TH). This, in turn, necessitates a tightly regulated expression of TH signaling components such as TH transporters, deiodinases, and TH receptors in a brain region- and cell-specific manner from early developmental stages onwards. Abnormal TH levels during critical stages, as well as mutations in TH signaling components that alter the global and/or local thyroidal state, result in detrimental consequences for brain development and neurological functions that involve alterations in central neurotransmitter systems. Thus, the question as to how TH signaling is implicated in the development and maturation of different neurotransmitter and neuromodulator systems has gained increasing attention. In this review, we first summarize the current knowledge on the regulation of TH signaling components during brain development. We then present recent advances in our understanding on how altered TH signaling compromises the development of cortical glutamatergic neurons, inhibitory GABAergic interneurons, cholinergic and dopaminergic neurons. Thereby, we highlight novel mechanistic insights and point out open questions in this evolving research field.

Nutritional management and interventions in complications of pregnancy: A systematic review

Background: Pregnancy, also known as the "gestation period" which lasts for 37-40 weeks, has been marked as the period of "physiological stress" in a woman's life. A wide range of symptoms, from nausea to ectopic pregnancy, are usually aligned with risk factors like abortion, miscarriage, stillbirth, etc. An estimated total of 15% of total pregnant women face serious complications requiring urgent attention for safe pregnancy survival. Over the past decades, several changes in the environment and nutrition habits have increased the possibility of unfavourable changes during the gestation phase. The diagnostic factors, management and nutritional interventions are targeted and more emphasis has been laid on modifying or managing the nutritional factors in this physiologically stressed phase. Aims: This review focuses on dietary modifications and nutritional interventions for the treatment of complications of pregnancy. Nutritional management has been identified to be one of the primary necessities in addition to drug therapy. It is important to set a healthy diet pattern throughout the gestation phase or even before by incorporating key nutrients into the maternal diet. Methods: The published literature from various databases including PubMed, Google Scholar and ScienceDirect were used to establish the fact of management and treatment of complications of pregnancy. Results: The recommendations of dietary supplements have underlined the concept behind the eradication of maternal deficiencies and improving metabolic profiles. Conclusion: Therefore, the present review summarises the dietary recommendations to combat pregnancy-related complications which are necessary in order to prevent and manage the same.

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.

Women With Chronic Hypoparathyroidism Have Low Risk of Adverse Pregnancy Outcomes

CONTEXT

There are scarce data on the management of chronic hypoparathyroidism (hypoPT) in pregnant women.

OBJECTIVE

The aim of this study was to evaluate pregnancy outcome and total number of births in maternal chronic hypoPT.

METHODS

The Swedish National Patient Register, The Swedish Prescribed Drug Register, Swedish Medical Birth Register, and the Total Population Register were used to identify 97 women with chronic hypoPT and 1030 age-matched controls who delivered 139 and 1577 singleton infants, respectively, following diagnosis between 1997 and 2017.

RESULTS

Women in the chronic hypoPT group had more frequent diabetes (DM) and chronic kidney disease (CKD) compared with the control group (P = 0.043 and P < 0.001, respectively). After adjusting for DM, CKD, maternal age at delivery, and calendar year of delivery, chronic hypoPT cases were associated with increased risk of induction of labor (OR, 1.82; 95% CI, 1.13-2.94) and birth of infants with lower birth weight (β-coefficient -188 g; 95% CI, -312.2 to -63.8) compared with controls. No difference was found in infant length, small for gestational age, or head circumference after adjustments. Mean gestational age at delivery after controlling for DM, CKD, and pre-eclampsia was not significantly younger (P = 0.119). There was no difference in congenital malformations or perinatal death and no difference in the total number of infants born between groups (P = 0.518).

CONCLUSION

The majority of women with chronic hypoPT had normal pregnancy outcomes, and the overall risks appear low. Maternal chronic hypoPT is, however, associated with higher risk of induction of labor and slightly lower infant birth weight.

Maternal Hypothyroidism Increases the Risk of Attention-Deficit Hyperactivity Disorder in the Offspring

OBJECTIVE

This study aimed to determine if hypothyroidism prior to, or during, pregnancy increases the risk of attention-deficit hyperactivity disorder (ADHD) in the child and how the association may be modified by preterm birth, sex of the child, and race-ethnicity.

STUDY DESIGN

Data were abstracted from linked maternal-child medical records. Incidence rate differences (IRDs), adjusted hazard ratios (aHRs), and their 95% confidence intervals (CIs) were estimated to evaluate the association of maternal hypothyroidism with childhood ADHD risk. Stratified analyses were used to evaluate whether the association is affected by timing of first diagnosis, gestational age at birth (term vs. preterm), sex, and race-ethnicity.

RESULTS

Hypothyroidism diagnosed prior to (IRD = 1.30), or during (IRD = 0.59) pregnancy increases the risk of ADHD in the children (aHR = 1.27; 95% CI: 1.15, 1.41, and 1.17; 95% CI: 1.00, 1.38). The association was strongest when diagnosed during the first trimester (IRD = 0.97 and aHR = 1.28; 95% CI: 1.04, 1.58). For children born preterm, there was significantly increased risk of ADHD if their mothers were diagnosed prior to (IRD = 3.06 and aHR = 1.43; 95% CI: 1.09, 1.88), but not during pregnancy. The effect of maternal hypothyroidism on increased risk of ADHD was stronger for boys (IRD = 1.84 and aHR = 1.26; 95% CI: 1.14, 1.40) than it was for girls (IRD = 0.48 and aHR = 1.19; 95% CI: 1.01, 1.40) and for Hispanic children (IRD = 1.60 and aHR = 1.45; 95% CI: 1.25, 1.68) compared with other race ethnicities.

CONCLUSION

Exposure to maternal hypothyroidism during the periconceptual period significantly increases the risk of ADHD and that the association varies with gestational age at delivery, child sex, and race-ethnicity.

KEY POINTS

· Maternal hypothyroidism increases the risk of ADHD diagnosis in the offspring.. · The association of maternal hypothyroidism with childhood ADHD was influenced by timing of diagnosis.. · Strength of the association was strongest in preterm born infants, boys, and Hispanic children..

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

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

Maternal Thyroid Dysfunction During Pregnancy and the Risk of Adverse Outcomes in the Offspring: A Systematic Review and Meta-Analysis

CONTEXT

Previous studies suggested a potential link of maternal thyroid dysfunction with adverse neurocognitive outcomes and impaired development of internal organs in offspring.

OBJECTIVE

To review the association between maternal thyroid dysfunction and the risk of adverse outcomes in offspring.

DATA SOURCES

PubMed, EMBASE, and Cochrane Library.

STUDY SELECTIONS

Eligible studies reported the association between maternal thyroid hormone function and the risk of adverse outcomes in their children.

DATA EXTRACTION

Reviewers extracted data on study characteristics and results independently.

DATA SYNTHESIS

Estimates were pooled and reported as odds ratio (OR) with 95% confidence interval (CI). I2 tests were applied to assess the heterogeneity across studies.

RESULTS

We identified 29 eligible articles and found an association between maternal hyperthyroidism and attention deficit hyperactivity disorder (ADHD) (OR: 1.18, 95% CI: 1.04-1.34, I2 = 0%) and epilepsy (OR: 1.19, 95% CI: 1.08-1.31, I2 = 0%) in offspring; as well as an association of maternal hypothyroidism with increased risk of ADHD (OR: 1.14, 95% CI: 1.03-1.26, I2 = 25%), autism spectrum disorder (OR: 1.41, 95% CI: 1.05-1.90, I2 = 63%), and epilepsy (OR: 1.21, 95% CI: 1.06-1.39, I2 = 0%) in offspring.

CONCLUSION

Routine measurement and timely treatment on thyroid function should be considered for pregnant women.

The chance of a live birth after assisted reproduction in women with thyroid disorders

PURPOSE

Women with thyroid disorders may have increased infertility and poor reproductive outcomes, but it is unclear if assisted reproductive technology (ART) is effective in this population. The aim of this study was to examine the chance of a pregnancy (biochemical and clinical), and a live birth after ART, in women with thyroid disorders undergoing ART treatment, compared to women without thyroid disorders. Among live-born children, we assessed the risk of congenital malformations.

PATIENTS AND METHODS

In a nationwide cohort study of all women undergoing ART treatments in Denmark from 1 January 1994 throughout June 2017, we calculated the chance of a pregnancy and a live birth after embryo transfer. Women with thyroid disorders were stratified into two groups: those diagnosed with hypothyroid or hyperthyroid disorders. The adjusted OR (aOR) of a biochemical and a clinical pregnancy, a live born child and a congenital malformation was computed using multilevel logistic regression models.

RESULTS

In total, 199,674 embryo transfers were included in 2,101 women with thyroid disorders and in 65,526 women without thyroid disorders. The chance of a biochemical pregnancy was significantly reduced in women with hyperthyroidism (aOR=0.80, 95% CI 0.69-0.93), and the aOR of a live birth was 0.86, 95% CI 0.76-0.98. The aOR for a live birth in women with hypothyroidism was 1.03 (95% CI 0.94-1.12). Children of women with hypothyroidism, who were conceived after ART treatment, had a significantly increased risk of any congenital malformation (aOR=1.46 [95% CI 1.07-2.00]).

CONCLUSION

Women with hyperthyroidism receiving ART treatment had a decreased chance of a live birth per embryo transfer compared to women without thyroid disorders. Women with hypothyroidism did not have a decreased chance of a live birth but their offspring had an increased risk of congenital malformation.

Fluoride Exposure Induces Inhibition of Sodium-and Potassium-Activated Adenosine Triphosphatase (Na+, K+-ATPase) Enzyme Activity: Molecular Mechanisms and Implications for Public Health

In this study, several lines of evidence are provided to show that Na + , K + -ATPase activity exerts vital roles in normal brain development and function and that loss of enzyme activity is implicated in neurodevelopmental, neuropsychiatric and neurodegenerative disorders, as well as increased risk of cancer, metabolic, pulmonary and cardiovascular disease. Evidence is presented to show that fluoride (F) inhibits Na + , K + -ATPase activity by altering biological pathways through modifying the expression of genes and the activity of glycolytic enzymes, metalloenzymes, hormones, proteins, neuropeptides and cytokines, as well as biological interface interactions that rely on the bioavailability of chemical elements magnesium and manganese to modulate ATP and Na + , K + -ATPase enzyme activity. Taken together, the findings of this study provide unprecedented insights into the molecular mechanisms and biological pathways by which F inhibits Na + , K + -ATPase activity and contributes to the etiology and pathophysiology of diseases associated with impairment of this essential enzyme. Moreover, the findings of this study further suggest that there are windows of susceptibility over the life course where chronic F exposure in pregnancy and early infancy may impair Na + , K + -ATPase activity with both short- and long-term implications for disease and inequalities in health. These findings would warrant considerable attention and potential intervention, not to mention additional research on the potential effects of F intake in contributing to chronic disease.

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 hypothyroidism and future pediatric neurological morbidity of the offspring

BACKGROUND

Maternal hypothyroidism in pregnancy has been associated with neurocognitive impairment in exposed children, ranging from psychomotor-developmental delay to lower IQ scores.

OBJECTIVE

To investigate the long-term neurological morbidity of children to hypothyroid mothers during pregnancy.

STUDY DESIGN

A population-based cohort study was performed including all deliveries occurring in a period of 20 years at a tertiary medical center. We excluded multiple pregnancies, fetuses with congenital malformations, perinatal mortality cases and women lacking prenatal care from the study. Neurological-related hospitalizations of children (up to 18 years) were evaluated using neurological morbidities that were predefined by ICD-9 codes. Kaplan-Meier survival curve was used to compare cumulative hospitalization rate in exposed and unexposed children. A Cox regression model was used to control for confounders.

RESULTS

During the study period, 217,910 deliveries met the inclusion criteria. Of them, 1.1% (n = 2403) were in mothers with known hypothyroidism during pregnancy. The Kaplan-Meier survival curve demonstrated a significantly higher cumulative incidence of neurological-related hospitalizations in the hypothyroidism group (log rank p = 0.007). Total hospitalization rate per person years was significantly higher in the maternal hypothyroidism group (5.5 vs. 3.1, HR =1.37, 95% CI 1.10-1.73, p = 0.007). The Cox regression model controlled for various possible confounders including maternal age, maternal obesity, birth weight, preterm birth, maternal diabetes, hypertensive disorders, induction of labor and mode of delivery, found maternal hypothyroidism to be independently associated with pediatric neurological morbidity in these children (adjusted HR =1.33, 95% CI 1.05-1.68, p = 0.01).

CONCLUSION

Maternal hypothyroidism in pregnancy is independently associated with long-term pediatric neurological morbidity of the offspring.

Effect of Thyroid Hormones on Neurons and Neurodevelopment

This review focuses on the current knowledge of the effects of thyroid hormones on central nervous system differentiation and development in animals and the human fetal brain. The outcomes of children with congenital hypothyroidism and of newborns with hypothyroid pregnant mothers are emphasized, focusing on how therapies could affect and especially improve the outcomes.

Chronic diseases in the children of women with maternal thyroid dysfunction: a nationwide cohort study

Objective

Maternal thyroid disease (TD) during pregnancy is associated with adverse birth outcomes, but little is known on its long-term outcomes. We aimed to examine if children born to mothers with TD have increased disease risk during childhood and adolescence.

Patients and methods

A register-based cohort study was conducted on all live born children in Denmark from 1989 to 2013, including the association between maternal TD during pregnancy and somatic and psychiatric diseases in the children. Cox proportional hazards models were used to compute hazard ratios (HRs) according to the type of maternal TD, Graves’ disease, and Hashimoto’s thyroiditis.

Results

A total of 2,618 children were born to women with Graves’ disease, 760 to women with Hashimoto’s thyroiditis (exposed), and 1,557,577 to women without any TD (unexposed). The median follow-up time for children born to mothers with Graves’ disease was 9.3 years (25/75 percentile 5.4/13.9 years) and with Hashimoto’s thyroiditis was 4.8 years (25/75 percentile 2.5/8.2 years). In children exposed to maternal Graves’ disease in utero, the adjusted HR of TD was 12.83 (95% CI, 9.74–16.90), Graves’ disease was 34.3 (95% CI, 20.23–58.35), and type 1 was diabetes 2.47 (95% CI, 1.46–4.18). In children exposed to maternal Hashimoto’s thyroiditis, the adjusted HR of Hashimoto’s thyroiditis was 24.04 (95% CI, 5.89–97.94).

Conclusion

Our data suggest that children born to women with Graves’ disease and Hashimoto’s thyroiditis have excess long-term morbidities in childhood and adolescence. We particularly found an increased risk of any TD and type 1 diabetes to be diagnosed in children exposed in utero to Graves’ disease. These novel findings are relevant for pediatricians, stressing the importance of history of maternal disease when evaluating children with suspected endocrine disorders.

Maternal thyroid disorder in pregnancy and risk of cerebral palsy in the child: a population-based cohort study

Background

Cerebral palsy is the most frequent motor disability in childhood, but little is known about its etiology. It has been suggested that cerebral palsy risk may be increased by prenatal thyroid hormone disturbances. The objective of this study was to investigate whether maternal thyroid disorder is associated with increased risk of cerebral palsy.

Methods

A population-based cohort study using two study populations. 1) 1,270,079 children born in Denmark 1979–2007 identified in nationwide registers, and 2) 192,918 children born 1996–2009 recruited into the Danish National Birth Cohort and The Norwegian Mother and Child Cohort study, combined in the MOthers and BAbies in Norway and Denmark (MOBAND) collaboration cohort. Register-based and self-reported information on maternal thyroid disorder was studied in relation to risk of cerebral palsy and its unilateral and bilateral spastic subtypes using multiple logistic regression. Children were followed from the age of 1 year to the age of 6 years, and cerebral palsy was identified in nationwide registers with verified diagnoses.

Results

In register data, hypothyroidism was recognized in 12,929 (1.0%), hyperthyroidism in 9943 (0.8%), and unclassifiable thyroid disorder in 753 (< 0.1%) of the mothers. The odds ratio for an association between maternal thyroid disorder and bilateral spastic cerebral palsy was 1.0 (95% CI: 0.7–1.5). Maternal thyroid disorder identified during pregnancy was associated with elevated risk of unilateral spastic cerebral palsy (odds ratio 3.1 (95% CI: 1.2–8.4)). In MOBAND, 3042 (1.6%) of the mothers reported a thyroid disorder in pregnancy, which was not associated with cerebral palsy overall (odds ratio 1.2 (95% CI: 0.6–2.4)).

Conclusions

Maternal thyroid disorder overall was not related to bilateral spastic cerebral palsy, but maternal thyroid disorder identified in pregnancy was associated with increased risk of unilateral spastic cerebral palsy. These findings should be replicated in studies making use of maternal blood samples.

Electronic supplementary material

The online version of this article (10.1186/s12887-018-1152-5) contains supplementary material, which is available to authorized users.

Maternal Thyroid Function in Early Pregnancy and Child Neurodevelopmental Disorders: A Danish Nationwide Case-Cohort Study

BACKGROUND

Maternal thyroid dysfunction may adversely affect fetal brain development, but more evidence is needed to refine this hypothesis. The aim of this study was to evaluate potential fetal programming by abnormal maternal thyroid function on child neurodevelopmental disorders.

METHODS

The design was a case-cohort study within the Danish National Birth Cohort (1997-2003). From the eligible cohort of 71,706 women, a random 12% sub-cohort (n = 7624) was selected, and all women (n = 2276) whose child was diagnosed with seizures, specific developmental disorder (SDD), autism spectrum disorder (ASD), and/or attention-deficit/hyperactivity disorder (ADHD) up to December 31, 2010, were identified. All women had a blood sample drawn in early pregnancy (median week 9), and the stored sample was used for measurement of free thyroxine and thyrotropin. Method- and week-specific reference ranges were used for classification of maternal thyroid function. A weighted Cox proportional hazards model was used to estimate adjusted hazard ratio (aHR) with 95% confidence intervals (CI) for neurodevelopmental disorders in children exposed to maternal thyroid dysfunction.

RESULTS

The overall frequency of abnormal maternal thyroid function was 12.5% in the sub-cohort and significantly higher among cases of ASD (17.9%; aHR = 1.5 [CI 1.1-2.1]), but not among other types of neurodevelopmental disorders (febrile seizures: 12.7%; epilepsy: 13.1%; SDD: 12.6%; and ADHD: 14.0%). However, evaluation of subtypes of maternal thyroid dysfunction showed that maternal overt hypothyroidism (thyrotropin >10 mIU/L) was a risk factor for epilepsy in the child (aHR = 3.5 [CI 1.2-10]), as was overt hyperthyroidism for cases diagnosed within the first year of life (aHR = 3.0 [CI 1.03-8.4]). Furthermore, both maternal hypothyroidism (aHR = 1.8 [CI 1.1-2.7]) and overt hyperthyroidism (aHR = 2.2 [CI 1.1-4.4]) were risk factors for ASD in the child, and isolated low free thyroxine was associated with ASD (aHR = 4.9 [CI 2.03-11.9]) and ADHD (aHR = 2.3 [CI 1.2-4.3]) in girls but not in boys.

CONCLUSIONS

Abnormal maternal thyroid function in early pregnancy was associated with epilepsy, ASD, and ADHD in the child, but associations differed by subtypes of exposure and by child age and sex. More evidence on subtypes and severity of maternal thyroid function is needed, and alternative outcomes of child neurodevelopment may be warranted.

Maternal hormonal milieu influence on fetal brain development

An adverse maternal hormonal environment during pregnancy can be associated with abnormal brain growth. Subtle changes in fetal brain development have been observed even for maternal hormone levels within the currently accepted physiologic ranges. In this review, we provide an update of the research data on maternal hormonal impact on fetal neurodevelopment, giving particular emphasis to thyroid hormones and glucocorticoids. Thyroid hormones are required for normal brain development. Despite serum TSH appearing to be the most accurate indicator of thyroid function in pregnancy, maternal serum free T4 levels in the first trimester of pregnancy are the major determinant of postnatal psychomotor development. Even a transient period of maternal hypothyroxinemia at the beginning of neurogenesis can confer a higher risk of expressive language and nonverbal cognitive delays in offspring. Nevertheless, most recent clinical guidelines advocate for targeted high-risk case finding during first trimester of pregnancy despite universal thyroid function screening. Corticosteroids are determinant in suppressing cell proliferation and stimulating terminal differentiation, a fundamental switch for the maturation of fetal organs. Not surprisingly, intrauterine exposure to stress or high levels of glucocorticoids, endogenous or synthetic, has a molecular and structural impact on brain development and appears to impair cognition and increase anxiety and reactivity to stress. Limbic regions, such as hippocampus and amygdala, are particularly sensitive. Repeated doses of prenatal corticosteroids seem to have short-term benefits of less respiratory distress and fewer serious health problems in offspring. Nevertheless, neurodevelopmental growth in later childhood and adulthood needs further clarification. Future studies should address the relevance of monitoring the level of thyroid hormones and corticosteroids during pregnancy in the risk stratification for impaired postnatal neurodevelopment.

Causes and Factors Associated with Neonatal Seizure and its Short-term Outcome: A Retrospective Prognostic Cohort Study

OBJECTIVE

Neonatal seizures are common, difficult to diagnose and treat, and associated with a great mortality rate and long-term risk of neurodevelopmental impairments. We aimed to determine the etiology, clinical presentation, and neurodevelopmental outcome of neonatal seizures.

MATERIALS AND METHODS

In this cross-sectional study, 88 neonates, aged < 28 days, admitted to Mofid Children's Hospital, Tehran, Iran, from September 2011 to 2013 with the initial diagnosis of seizure were enrolled by convenient sampling method. Data, including age, gestational age, birth weight, Apgar of the fifth minute, neonatal intensive care unit (NICU) admission, family history, type, cause, and age of seizure, EEG and paraclinic findings, anticonvulsant used for treatment, neurodevelopmental status, and the final outcome, were collected from medical records and the missed cases were completed by phone calls. The frequency and association of variables were analyzed using SPSS software.

RESULTS

Among neonates with seizures, 67% were male, 79.5% were born term, and 72.7% had normal birth weight. The most common type of seizure was multifocal clonic seizures (45.5%). The main diagnosis in neonates with seizures was hypoxic-ischemic encephalopathy (HIE) (23.9%) and hypoglycemia (10.22%). The mortality rate was 11.36% during a mean follow-up period of 21.4±6.4 months. Neurodevelopmental assessments showed that 64% were normal, 27% had global delay, and 9% had motor delay. Positive family history of epilepsy (P=0.006), low Apgar score (P=0.002) and epilepsy (P<0.001) were significantly associated with adverse neurodevelopmental outcome.

CONCLUSION

Since HIE and hypoglycemia were the most common cause of neonatal seizures, efforts should be made to improve care during delivery and early breastfeeding.

MECHANISMS IN ENDOCRINOLOGY: Neurodevelopmental disorders in children born to mothers with thyroid dysfunction: evidence of fetal programming?

Fetal programming is a long-standing, but still evolving, concept that links exposures during pregnancy to the later development of disease in the offspring. A fetal programming effect has been considered within different endocrine axes and in relation to different maternal endocrine diseases. In this critical review, we describe and discuss the hypothesis of fetal programming by maternal thyroid dysfunction in the context of fetal brain development and neurodevelopmental disorders in the offspring. Thyroid hormones are important regulators of early brain development, and evidence from experimental and observational human studies have demonstrated structural and functional abnormalities in the brain caused by the lack or excess of thyroid hormone during fetal brain development. The hypothesis that such abnormalities introduced during early fetal brain development increase susceptibility for the later onset of neurodevelopmental disorders in the offspring is biologically plausible. However, epidemiological studies on the association between maternal thyroid dysfunction and long-term child outcomes are observational in design, and are challenged by important methodological aspects.

Early Pregnancy Thyroid Function Test Abnormalities in Biobank Sera from Women Clinically Diagnosed with Thyroid Dysfunction Before or After Pregnancy

BACKGROUND

Maternal thyroid disease may complicate pregnancy. A high frequency of abnormal thyroid function test results in pregnant women with known thyroid disease has been reported, but the frequency of unidentified thyroid dysfunction in women first clinically diagnosed with thyroid disease after a pregnancy is not known.

METHODS

This was a population-based study of pregnant women in the Danish National Birth Cohort (DNBC) who had a blood sample drawn in early pregnancy and terminated the pregnancy with a singleton live-birth in the period between 1997 and 2003. Participants were all women in the DNBC who had a registration of thyroid disease before and/or up to five years after the pregnancy in nationwide health registers (n = 2445) and a 12% random sample of all women in the cohort (n = 7624). Thyrotropin and free thyroxine were measured with an immunoassay in sera stored in the Danish National Biobank. Method- and pregnancy week-specific references ranges were used for classification of thyroid function test abnormalities.

RESULTS

The frequency of abnormal thyroid function in early pregnancy was 12.5% in the random sample and 35.7% among women clinically diagnosed with thyroid disease before or after blood sampling (55.7% among women on current treatment). One third of women clinically diagnosed with thyroid disease after blood sampling had unidentified thyroid dysfunction in the early pregnancy blood sample (most frequently [52.0%] unidentified hypothyroidism in women with a later diagnosis of hypothyroidism).

CONCLUSIONS

More than 50% of Danish pregnant women on current treatment for thyroid disease had thyrotropin and/or free thyroxine outside the week-specific reference ranges, and the frequency of unidentified early pregnancy thyroid dysfunction in women clinically diagnosed after the pregnancy was also high.

Managing hyperthyroidism in pregnancy: current perspectives

Hyperthyroidism in women who are of childbearing age is predominantly of autoimmune origin and caused by Graves' disease. The physiological changes in the maternal immune system during a pregnancy may influence the development of this and other autoimmune diseases. Furthermore, pregnancy-associated physiological changes influence the synthesis and metabolism of thyroid hormones and challenge the interpretation of thyroid function tests in pregnancy. Thyroid hormones are crucial regulators of early development and play an important role in the maintenance of a normal pregnancy and in the development of the fetus, particularly the fetal brain. Untreated or inadequately treated hyperthyroidism is associated with pregnancy complications and may even program the fetus to long-term development of disease. Thus, hyperthyroidism in pregnant women should be carefully managed and controlled, and proper management involves different medical specialties. The treatment of choice in pregnancy is antithyroid drugs (ATDs). These drugs are effective in the control of maternal hyperthyroidism, but they all cross the placenta, and so need careful management and control during the second half of pregnancy considering the risk of fetal hyper- or hypothyroidism. An important aspect in the early pregnancy is that the predominant side effect to the use of ATDs in weeks 6-10 of pregnancy is birth defects that may develop after exposure to available types of ATDs and may be severe. This review focuses on four current perspectives in the management of overt hyperthyroidism in pregnancy, including the etiology and incidence of the disease, how the diagnosis is made, the consequences of untreated or inadequately treated disease, and finally how to treat overt hyperthyroidism in pregnancy.

Maternal thyroid function in pregnancy may program offspring blood pressure, but not adiposity at 20 y of age

BACKGROUND

Experimental evidence exists indicating that maternal thyroid hormones during pregnancy may affect the metabolic set point and cardio-vascular function in the offspring. The objective of this study was to investigate the association between maternal thyroid function in week 30 of gestation and offspring adiposity and blood pressure at 20 y.

METHODS

The study was based on the follow up of a Danish birth cohort from 1988 to 1989 (n = 965). A blood sample was drawn from the pregnant women in week 30 of gestation (N = 877). In 2008-2009, the offspring were followed up with self-reported anthropometrics (N = 645) and a clinically measured blood pressure (N = 425). Multiple linear regressions were used to estimate the association between maternal thyroid function and offspring BMI, waist circumference, and blood pressure.

RESULTS

Offspring of subclinical hypothyroid women had higher systolic blood pressure (adjusted difference = 3.6, 95% confidence interval: 0.2, 7.0 mmHg) and a tendency toward higher diastolic blood pressure (adjusted difference = 2.3, 95% confidence interval: -0.2, 4.9 mmHg) compared to offspring of euthyroid women. No association was found with offspring BMI and waist circumference.

CONCLUSION

Maternal thyroid function during third trimester of pregnancy may affect long-term blood pressure in the offspring.

Foetal programming by maternal thyroid disease

Foetal programming is an emerging concept that links a wide range of exposures during foetal life to later development of disease. Thyroid disorders are common in women of reproductive age, and careful management of pregnant women suffering from thyroid disease is important considering the crucial role of thyroid hormones during early brain development. It is possible that maternal thyroid dysfunction in pregnancy may lead to structural and/or functional changes during foetal brain development. Such an effect could later predispose the offspring to an increased risk of neurologic or psychiatric disease. We recently observed that children born to mothers with thyroid dysfunction had an increased risk of developing seizure disorders, autism spectrum disorders, attention-deficit hyperactivity disorders and psychiatric disease in adolescence and young adulthood. In the review, we discuss the concept of potential foetal programming by maternal thyroid disease.