Maternal thyroid dysfunction during pregnancy and thyroid function of her child in adolescence

Association of Maternal TSH, FT4 With Children's BMI Trajectories, and Obesity: A Birth Cohort Study

OBJECTIVE

To investigate the association between maternal TSH, free thyroxine (FT4), and children's body mass index (BMI) trajectories and obesity.

METHOD

Based on the Ma'anshan Birth Cohort in China, we repeatedly assayed maternal thyroid functions in 3 trimesters of pregnancy. Children's height and weight were measured 15 times before they were age 6 years. Body fat was assessed when children were aged 6 years. Mplus software was used to fit maternal thyroid hormone trajectories and BMI trajectories. Multivariate logistic regression models and generalized linear models were used in data analysis.

RESULTS

Low maternal FT4 trajectory was observed to be related to an increased risk of a high children's BMI trajectory and overweight, with an odds ratio and 95% CI of 1.580 (1.169-2.135) and 1.505 (1.064-2.129), respectively. Increased maternal FT4 concentrations in the first, second, and third trimesters were associated with a decreased risk of high children's BMI trajectories and obesity. There was a positive association between low maternal FT4 trajectory and 6-year-old children's body fat ratio with β and 95% CI of 0.983 (0.138-1.829). Furthermore, negative correlations between maternal FT4 concentration in the first, second, and third trimesters of pregnancy and body fat ratio were observed.

CONCLUSIONS

Low maternal FT4 trajectory during pregnancy may predict a high BMI trajectory in children and relate to overweight and high body fat ratio in 6-year-old children. High maternal FT4 concentrations throughout pregnancy may be associated with the decreasing risk of obesity and low body fat ratio in 6-year-old children.

Developmental scores in offspring of women with subclinical hypothyroidism in pregnancy are affected by gender and thyrotropin cutoff

OBJECTIVES

Subclinical hypothyroidism (SCH) is defined by elevated thyrotropin (TSH) and normal level of thyroxine (T4). The definition of SCH and the cutoff for TSH normality in pregnancy are debated. In the present study, we assess offspring perinatal outcome, anthropometrics and early development in relation to different TSH levels.

METHODS

An observational study with 77 singleton-pregnant women included by thyroid screening before a planned cesarean section. Two TSH-cutoffs (3.0 and 3.7 mIU/L) defined euthyroid and SCH groups, and were applied to evaluate offspring anthropometrics, complication rates (maternal blood loss, Apgar-score, cord arterial-pH, admission to neonatal intensive care unit, perinatal hypoglycemia) and offspring development. Development was evaluated by Bayley-III test in a subsample at age 6 months (n=27) and 15 months (n=22).

RESULTS

Prevalence of SCH was 31.2 % at TSH-cutoff 3.0 mIU/L, and 16.9 % at TSH-cutoff 3.7 mIU/L. No differences in complications and anthropometrics were observed. In Bayley-III tests, cognitive score was decreased at 6 months (p=0.012) and at 15 months (p=0.056) by applying TSH-cutoff 3.0 mIU/L. At cutoff 3.7 mIU/L, motor score was decreased at 15 months (p=0.020). Male offspring had significantly lower cognitive scores at age 6 and 15 months (TSH-cutoff 3.0 mIU/L), and motor scores at age 15 months (TSH-cutoff 3.7 mIU/L).

CONCLUSIONS

The importance of the definition of thyroid normality in pregnancy is underlined. This study suggests that a gender-effect might be present in maternal thyroid disease, and that developmental differences exist if TSH-cutoff is low. Further research is needed.

Pregnancy outcomes and neonatal thyroid function in women with thyroid cancer: a retrospective study

BACKGROUND

Evidence regarding adverse pregnancy outcomes in patients with thyroid cancer has been conflicting, and the effect of thyroid dysfunction caused by thyroid hormone suppression therapy in terms of neonatal thyroid stimulating hormone (TSH) is unclear. This study aimed to investigate whether thyroid cancer was associated with adverse pregnancy outcomes and had an adverse effect on neonatal thyroid function.

METHODS

This was a retrospective study of 212 singleton pregnancies with thyroid cancer and 35,641 controls without thyroid cancer. Data on maternal pregnancy outcomes and neonatal outcomes were analyzed.

RESULTS

The median TSH level in the thyroid cancer group was significantly lower than that in the control group (0.87 µIU/mL vs. 1.17 µIU/mL; P < 0.001), while the FT4 level was higher than that in the control group (17.16 pmol/L vs. 16.33 pmol/L; P < 0.001). The percentage of thyroid peroxidase antibodies (TPOAb) positive in the thyroid cancer group was significantly higher than that in the control group (25.0% vs. 11.8%; P < 0.001). Pregnancies with thyroid cancer had a higher risk of late miscarriage (OR 7.166, 95% CI: 1.521, 33.775, P = 0.013), after adjusting maternal TPOAb positive, there was no statistical significance (OR 3.480, 95% CI: 0.423, 28.614, P = 0.246). Pregnancies with thyroid cancer had higher gestational weight gain (GWG) (14.0 kg vs. 13.0 kg, P < 0.001). Although there was no significant difference in the prevalence of gestational diabetes mellitus (GDM) (20.8% vs. 17.4%, P = 0.194), the oral glucose tolerance test (OGTT) showed that fasting plasma glucose and 2-hour value in the thyroid cancer group were higher than those in the control group (P = 0.020 and 0.004, respectively). There was no statistically significant difference in TSH between the thyroid cancer group and the control group, regardless of full-term newborns or preterm newborns.

CONCLUSIONS

Thyroid cancer might not have substantial adverse effects on pregnancy outcomes except for excessive GWG. No adverse effect on neonatal TSH was found, but the effect on long-term thyroid function and neuropsychological function in offspring need further study.

TRIAL REGISTRATION

Beijing Birth Cohort Study (ChiCTR220058395).

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.

Euthyroid Thyroperoxidase Antibody Positivity during Pregnancy, to Treat or Not to Treat?

Thyroperoxidase antibody (TPOAb) positivity is a well-known risk factor for thyroid dysfunction during pregnancy and is associated with a suboptimal response to thyroidal stimulation by human chorionic gonadotropin. About 75% of TPOAb positive women are euthyroid and there seems to be a higher risk of predominantly miscarriage and preterm birth in this subgroup. Nonetheless, clinical decision making with regards to gestational levothyroxine treatment remains difficult due to a lack of large randomized trials. Future studies assessing dose-dependent associations and additional biomarkers that can distinguish low-risk from high-risk individuals will be key in disentangling the crude clinical data.

Maternal health, in-utero, and perinatal exposures and risk of thyroid cancer in offspring: a Nordic population-based nested case-control study

BACKGROUND

Thyroid cancer tends to be diagnosed at a younger age (median age 51 years) compared with most other malignancies (such as breast cancer [62 years] or lung cancer [71 years]). The incidence of thyroid cancer is higher in women than men diagnosed from early adolescence. However, few in-utero and early life risk exposures associated with increased risk of thyroid cancer have been identified.

METHODS

In this population-based nested case-control study we used registry data from four Nordic countries to assess thyroid cancer risk in offspring in relation to maternal medical history, pregnancy complications, and birth characteristics. Patient with thyroid cancer (cases) were individuals born and subsequently diagnosed with first primary thyroid cancer from 1973 to 2013 in Denmark, 1987 to 2014 in Finland, 1967 to 2015 in Norway, or 1973 to 2014 in Sweden. Each case was matched with up to ten individuals without thyroid cancer (controls) based on birth year, sex, country, and county of birth. Cases and matched controls with a previous diagnosis of any cancer, other than non-melanoma skin cancer, at the time of thyroid cancer diagnosis were excluded. Cases and matched controls had to reside in the country of birth at the time of thyroid cancer diagnosis. Conditional logistic regression models were used to calculate odds ratios (ORs) with 95% CIs.

RESULTS

Of the 2437 cases, 1967 (81·4%) had papillary carcinomas, 1880 (77·1%) were women, and 1384 (56·7%) were diagnosed before age 30 years (range 0-48). Higher birth weight (OR per kg 1·14 [95% CI 1·05-1·23]) and congenital hypothyroidism (4·55 [1·58-13·08]); maternal diabetes before pregnancy (OR 1·69 [0·98-2·93]) and postpartum haemorrhage (OR 1·28 [1·06-1·55]); and (from registry data in Denmark) maternal hypothyroidism (18·12 [10·52-31·20]), hyperthyroidism (11·91 [6·77-20·94]), goiter (67·36 [39·89-113·76]), and benign thyroid neoplasms (22·50 [6·93-73·06]) were each associated with an increased risk of thyroid cancer in offspring.

INTERPRETATION

In-utero exposures, particularly those related to maternal thyroid disorders, might have a long-term influence on thyroid cancer risk in offspring.

FUNDING

Intramural Research Program of the National Cancer Institute (National Institutes of Health).

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.

Long term outcomes of infants born by mothers with thyroid dysfunction during pregnancy

According to Barker’s hypothesis, sub-optimal conditions during gestation might affect the predisposition for diseases in adulthood. Alteration in endocrine functions during pregnancy, such us thyroid function or glucose metabolism, are not exempt. It is well known that subclinical hypothyroidism and thyroperoxidase antibodies-positive euthyroidism during early pregnancy are associated with increased risk of gestational diabetes mellitus and both conditions influence pregnancy outcome and newborn development and metabolism at short and long terms. Fetal production of thyroid hormones starts from the 12th week of gestational age. The transplacental passage of maternal thyroxine (T4) is therefore essential for the fetal neurological development, especially during the first half of pregnancy. If this passage is interrupted, such as in premature birth, neonates are more susceptible to develop impaired thyroid function, because of physiological immaturity of their hypothalamic-pituitary-thyroid axis, acute illnesses and stressful events (sepsis, invasive procedures, drugs). The aim of this review is to investigate the short and long term effects of maternal dysthyroidisms on term and preterm newborns, with particular attention to the metabolic and thyroid consequences. Metabolic syndrome, higher body mass index and greater waist circumference, seem to be more prevalent in children of TPO-Ab-positive mothers. Maternal hypothyroidism may be associated with higher risk of gestational diabetes and adverse birth outcomes, such as preeclampsia, preterm delivery, fetal death and low birth weight offspring. In adulthood, preterm (< 37 weeks of gestational age) or low birth weight (<2.500 g) newborns seem to be more susceptible to develop gestational diabetes, preeclampsia, type 2 diabetes mellitus and behavioral alterations. (www.actabiomedica.it)

Maternal, cord, and three-year-old child serum thyroid hormone concentrations in the Health Outcomes and Measures of the Environment study

PURPOSE

Maternal thyroid function during pregnancy may influence offspring thyroid function, though relations between maternal and child thyroid function are incompletely understood. We sought to characterize relations between maternal, cord and child thyroid hormone concentrations in a population of mother-child pairs with largely normal thyroid function.

METHODS

In a prospective birth cohort, we measured thyroid hormone concentrations in 203 mothers at 16 gestational weeks, 273 newborns and 159 children at 3 years among participants in the Health Outcomes and Measures of the Environment (HOME) Study. We used multivariable linear regression to estimate associations of maternal thyroid hormones during pregnancy with cord serum thyroid hormones and also estimated associations of maternal and cord thyroid hormones with child thyroid-stimulating hormone (TSH).

RESULTS

Each doubling of maternal TSH was associated with a 16.4% increase of newborn TSH (95% CI: 3.9%, 30.5%), and each doubling of newborn TSH concentrations was associated with a 10.4% increase in child TSH concentrations at 3 years (95% CI: 0.1%, 21.7%). An interquartile range increase in cord FT4 concentrations was associated with an 11.7% decrease in child TSH concentrations at 3 years (95% CI: -20.2%, -2.3%).

CONCLUSIONS

We observed relationships between maternal, newborn and child thyroid hormone concentrations in the HOME Study. Our study contributes to understandings of interindividual variability in thyroid function among mother-child pairs, which may inform future efforts to identify risk factors for thyroid disorders or thyroid-related health outcomes.

Changes in Thyroid Function Across Adolescence: A Longitudinal Study

OBJECTIVE

There are no large, longitudinal studies of thyroid function across adolescence. The aims of this study were to examine longitudinal trends in thyrotropin (TSH), free triiodothyronine (fT3) and free thyroxine (fT4) and determine age-specific reference ranges.

METHODS

Thyroid function was assessed in 3415 participants in the Brisbane Longitudinal Twin Study at ages 12, 14, and 16, using the Abbott ARCHITECT immunoassay. Longitudinal analyses were adjusted for body mass index and puberty.

RESULTS

In girls, mean fT4 (± SE) increased between age 12 and 14 (by 0.30 ± 0.08 pmol/L; P < 0.001), while remaining unchanged in boys; from age 14 to 16, fT4 increased in both girls (by 0.42 ± 0.07 pmol/L; P < 0.001) and boys (0.64 ± 0.07 pmol/L, P < 0.001). There was a slight increase in fT3 from age 12 to 14 years in girls (by 0.07 ± 0.03 pmol/L; P = 0.042), with a more marked increase in boys (0.29 ± 0.03 pmol/L; P < 0.001), followed by a decrease from age 14 to 16 in both sexes (girls, by 0.53 ± 0.02 pmol/L; P < 0.001; boys, by 0.62 ± 0.03 pmol/L; P < 0.001). From age 12 to 14, TSH showed no significant change in girls or boys, then levels increased from age 14 to 16 in both sexes (in girls, by 4.9%, 95% CI: 2.4%-10.3%, P = 0.020; in boys, by 7.2%, 95% CI: 3.0%-11.6%, P = 0.001). Reference ranges differed substantially from adults, particularly for fT4 and fT3.

CONCLUSIONS

Thyroid function tests in adolescents display complex, sexually dimorphic patterns. Implementation of adolescence-specific reference ranges may be appropriate.

Graves' disease and pregnancy

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

Maternal Thyroid Function During Pregnancy and the Child's Linguistic and Sensory Development in the Northern Finland Birth Cohort 1986

BACKGROUND

Maternal hypothyroidism and hypothyroxinemia are associated with poor neuropsychological development in children. Previous research is lacking on whether maternal thyroid dysfunction affects sensory and linguistic development in childhood.

METHODS

The Northern Finland Birth Cohort 1986 included all births within a year (9,362 women, 9,479 children) from the two northernmost Finnish provinces. Maternal serum samples (n = 5,791) were obtained in early pregnancy and analyzed for TSH, free T4, and thyroid peroxidase antibodies (TPO-Abs). Five thousand three hundred and ninety-one parents evaluated their child's sensory and linguistic development at 7 years old via a questionnaire (excluding children with an intelligence quotient ≤85). The prevalence of sensory and linguistic impairments was compared between mothers with and without thyroid dysfunction.

RESULTS

There were no statistically significant differences in the prevalence of sensory or linguistic impairment between children of mothers with and without thyroid dysfunction. Children of hypothyroid and hypothyroxinemic mothers had an increased prevalence of vision impairment compared with those of euthyroid mothers (10.8 and 11.7%, respectively, versus 6.5%), but the difference was not significant. All results remained similar after excluding TPO-Ab-positive mothers and premature children.

CONCLUSION

We did not find an association between maternal thyroid dysfunction during pregnancy and sensory and linguistic development impairment in childhood. A somewhat higher prevalence of vision impairment was seen in children of hypothyroid and hypothyroxinemic mothers, which merits further research.

Childhood Thyroid Function Reference Ranges and Determinants: A Literature Overview and a Prospective Cohort Study

BACKGROUND

Reported cutoffs for childhood thyrotropin (TSH) and free thyroxine (fT4) reference ranges vary widely, and knowledge on the determinants of childhood thyroid function is sparse. This study aimed to summarize the existing studies on thyroid function reference ranges in children. Furthermore, the objective was to investigate the determinants of childhood TSH and fT4 concentration in a population based-prospective cohort.

METHODS

First, to identify studies on childhood thyroid reference ranges, The National Library of Medicine's PubMed, Embase, Ovid Medline, Web of Science, and Google Scholar databases were systematically searched. Second, in a non-selected sample of 4273 children (median age 6.0 years, range 4.9-9.1 years) from the cohort, the associations of age, sex, anthropometric characteristics, ethnicity, maternal education, and time and season at venipuncture were studied with TSH and fT4 concentrations. The study also investigated to what extent between-individual variations in the determinants of TSH and fT4 could influence the calculation of reference ranges.

RESULTS

Published reference ranges for TSH and fT4 differ per age range and within age ranges (cutoffs low TSH: 0.13 to >1 mIU/L; high TSH: 2.36 to >10 mIU/L; low fT4: 7.0 to >10 pmol/L; high fT4: 15.5 to >30 pmol/L). In the present cohort, weight, sex, and ethnicity were determinants of TSH (p ≤ 0.03) and fT4 concentrations (p ≤ 0.01), and height and time at venipuncture were determinants of TSH only (p < 0.0001). The between-individual variation depending on clinical determinants for TSH ranged between 0.64 and 0.96 mIU/L (total population 0.87 mIU/L) for the lower limit and 4.30 and 5.62 mIU/L (total population 5.20 mIU/L) for the upper limit, whereas for fT4, the lower limit ranged between 13.6 and 14.2 pmol/L (total population 13.8 pmol/L) and the upper limit ranged between 20.2 and 23.0 pmol/L (total population 20.8 pmol/L).

CONCLUSIONS

Considerable differences exist in the reported reference ranges for childhood TSH and fT4 across and within age ranges and assays. The present cohort shows only a minimal association between TSH and fT4, suggesting that the hypothalamus-pituitary-thyroid axis remains unaffected by thyroid interfering factors. Various determinants of TSH and fT4 in children were identified, which accounted for a considerable variation of reference range cutoffs.

Maternal Thyroid Antibodies Associates With Cardiometabolic Risk Factors in Children at the Age of 16

CONTEXT AND OBJECTIVE

The objective of this study was to determine the effects of maternal thyroid dysfunction or antibodies during pregnancy on the cardiometabolic risk factors in children.

DESIGN, SETTING, AND PARTICIPANTS

This prospective population-based cohort study, Northern Finland Birth Cohort 1986, included all pregnancies within a year in the area. Maternal serum samples were collected before the 20th week of gestation and analyzed for thyrotropin, free T4, thyroid-peroxidase antibodies (TPO-Abs), and thyroglobulin antibodies (Tg-Abs). Cardiometabolic risk factors in children at the age of 16 years were evaluated via blood sampling and clinical examination. Data were available for 3229 to 4176 mother-child pairs.

MAIN OUTCOME MEASURES

Waist circumference, blood pressure, lipids and lipoproteins, and insulin resistance were measured. Odds ratios (ORs) with 95% confidence intervals (CIs) of cardiometabolic risk factors in children with and without mothers with thyroid dysfunction or antibodies were calculated with logistic regression and adjusted for covariates.

RESULTS

Children of TPO-Ab-positive mothers had higher odds of metabolic syndrome (OR, 2.57; 95%, CI 1.26 to 5.25) and waist circumference indicative of metabolic syndrome (OR, 1.69; 95% CI, 1.14 to 2.50). They were also more likely to be overweight or obese (OR, 1.56; 95% CI, 1.04 to 2.34). Maternal thyroid dysfunction or Tg-Ab positivity did not associate with cardiometabolic risk factors in children.

CONCLUSION

Metabolic syndrome, greater waist circumference, and higher body mass index were more prevalent in children of TPO-Ab-positive mothers, indicating an adverse cardiovascular health profile.

Iodine status and thyroid function among Spanish schoolchildren aged 6-7 years: the Tirokid study

I deficiency is still a worldwide public health problem, with children being especially vulnerable. No nationwide study had been conducted to assess the I status of Spanish children, and thus an observational, multicentre and cross-sectional study was conducted in Spain to assess the I status and thyroid function in schoolchildren aged 6-7 years. The median urinary I (UI) and thyroid-stimulating hormone (TSH) levels in whole blood were used to assess the I status and thyroid function, respectively. A FFQ was used to determine the consumption of I-rich foods. A total of 1981 schoolchildren (52 % male) were included. The median UI was 173 μg/l, and 17·9 % of children showed UI<100 μg/l. The median UI was higher in males (180·8 v. 153·6 μg/l; P<0·001). Iodised salt (IS) intake at home was 69·8 %. IS consumption and intakes of ≥2 glasses of milk or 1 cup of yogurt/d were associated with significantly higher median UI. Median TSH was 0·90 mU/l and was higher in females (0·98 v. 0·83; P<0·001). In total, 0·5 % of children had known hypothyroidism (derived from the questionnaire) and 7·6 % had TSH levels above reference values. Median TSH was higher in schoolchildren with family history of hypothyroidism. I intake was adequate in Spanish schoolchildren. However, no correlation was found between TSH and median UI in any geographical area. The prevalence of TSH above reference values was high and its association with thyroid autoimmunity should be determined. Further assessment of thyroid autoimmunity in Spanish schoolchildren is desirable.

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

BACKGROUND

Maternal hypothyroidism and/or hypothyroxinemia have been associated with child's poor neuropsychological development, but the results have been inconsistent.

METHODS

The Northern Finland Birth Cohort 1986 included all expected births within a year (9362 women, 9479 children) from the two northernmost provinces of Finland. Maternal serum samples (n = 5791) were obtained in early pregnancy (M ± SD = 10.7 ± 2.8 weeks' gestation), and serum samples from their children were obtained at 16 years of age (n = 5829). All samples were analyzed for thyrotropin, free thyroxine (fT4), and thyroid peroxidase antibodies. The children's school performance was evaluated by their main teachers at eight years of age, as well as by the adolescents themselves at 16 years of age. Data on possible severe intellectual deficiency and mild cognitive limitation were collected from healthcare records and registries for all children. Logistic regression estimated the odds of poor school performance or severe intellectual deficiency/mild cognitive limitation associated with exposure to maternal thyroid dysfunction. The odds of poor school performance associated with the adolescents' own thyroid function at age 16 were also estimated. Results are presented as odds ratios (OR) with confidence intervals (CI), adjusted for maternal/family covariates and child's sex.

RESULTS

Girls of mothers with subclinical hypothyroidism had more self-evaluated difficulties in mathematics than did girls of euthyroid mothers (OR 1.62 [CI 1.06-2.49]). Boys of hypothyroxinemic mothers repeated a school class more often than did boys of euthyroid mothers (OR 5.46 [CI 1.19-25.06]). Adolescents of hyperthyroid mothers had increased odds of poor self-evaluated performance in mathematics (OR 1.61 [CI 1.01-2.49]). Maternal thyroid dysfunction did not increase the odds of a child having severe intellectual deficiency/mild cognitive limitation. At 16 years of age, girls with hyperthyroidism by laboratory measurements had more difficulties in Finnish language (OR 2.82 [CI 1.42-5.61]) than did euthyroid girls. Boys with hypothyroxinemia by laboratory measurement had higher odds of having difficulties in Finnish and/or mathematics (OR 2.13 [CI 1.26-3.62]) than did euthyroid boys.

CONCLUSIONS

Maternal thyroid dysfunction during early pregnancy was associated with poorer scholastic performance of the adolescent. Additionally, adolescents' own thyroid dysfunction was associated with difficulties in school performance assessed by self-evaluation.

Iron deficiency, an independent risk factor for isolated hypothyroxinemia in pregnant and nonpregnant women of childbearing age in China

CONTEXT

Isolated hypothyroxinemia during early pregnancy may irreversibly damage the neurodevelopment of offspring. However, the causes are not well clarified.

OBJECTIVE

To explore the association of iron deficiency (ID) with hypothyroid function of women in early pregnancy and nonpregnant women.

DESIGN

A total of 7953 pregnant women of ≤ 12 weeks gestation and 2000 childbearing-aged women were recruited. A subpopulation including 3340 pregnant women and 1052 nonpregnant women with sufficient iodine intake and negative thyroid peroxidase antibody were studied. Mild and severe cases of hypothyroxinemia were defined as free T4 levels below the 10th percentile and the 5th percentile, respectively, with normal TSH. Total body iron, serum ferritin, and serum transferrin receptor were used as indicators for iron nutrition.

RESULTS

Serum free T4 levels were significantly lower in both pregnant and nonpregnant women with ID compared with the corresponding groups without ID (both P < .05). The prevalence of mild and severe hypothyroxinemia was markedly higher in women with ID than those without, in both pregnant and nonpregnant women (all P < .01). Logistic regression indicated that ID was an independent risk factor for both mild and severe hypothyroxinemia in pregnancy (odds ratio [OR] = 2.440, 95% confidence interval [CI]: 1.324-4.496, P = .004; and OR = 3.278, 95% CI: 1.443-7.446, P = .005, respectively) and nonpregnancy (OR = 2.662, 95% CI: 1.330-5.329, P = .006; and OR = 3.254, 95% CI: 1.375-7.700, P = .007, respectively).

CONCLUSIONS

An association between ID and isolated hypothyroxinemia was found in both pregnant and nonpregnant childbearing-aged women, independent of the effects of iodine and thyroid autoimmunity. We speculate that ID may be a pathogenic factor for hypothyroxinemia, even in pregnant women during the first trimester.

Maternal thyroid autoantibody and elevated risk of autism in a national birth cohort

OBJECTIVE

Autoimmune disruption may contribute to risk for autism; however, since previous studies relied upon clinical diagnoses, exposure misclassification and recall bias are limitations. Thyroid peroxidase antibody (TPO-Ab) is an autoantibody involved in autoimmune thyroiditis. We aimed to test the a priori hypothesis that positivity to maternal serum TPO-Ab (TPO-Ab+) (defined as >156 IU/ml) during pregnancy is related to childhood autism.

METHOD

The study was based on a nested case-control design of the Finnish Prenatal Study of Autism (FiPS-A), a national birth cohort that includes prospectively drawn archived maternal serum specimens from virtually the entire pregnant population of Finland beginning in 1983. Cases of childhood autism (ICD-10F84.0) born from 1987 to 2005 were ascertained by performing linkages between national birth and inpatient/outpatient registries. All diagnosed cases in Finland over the birth years, and comparison subjects without ASD or severe/profound intellectual disability were matched 1:1 on date of birth, sex, birthplace, and residence in Finland. Maternal serum specimens were assayed in 967 matched case-control pairs for TPO-Ab by a chemiluminescent microparticle immunoassay blind to case/control status. Data were analyzed by conditional logistic regression for matched sets.

RESULTS

The prevalence of maternal TPO-Ab+ was significantly increased in pregnancies giving rise to autism cases (6.15%) compared to controls (3.54%). The odds of autism were increased by nearly 80% among offspring of mothers who were TPO-Ab+ during pregnancy (OR=1.78, 95% CI=1.16-2.75, p=0.009), compared to mothers negative for this autoantibody. There was also a significant relationship between maternal TPO-Ab defined as a continuous variable and odds of autism (OR=1.09, 95% CI=1.01, 1.17, p=0.02). Measures of maternal thyroid hormones did not differ between groups.

CONCLUSIONS

These findings provide the first biomarker-based evidence that a class of known maternal autoimmune disorders is related to autism in offspring.

Controversies in endocrinology: On the need for universal thyroid screening in pregnant women

There is a well-known controversy among scientific societies regarding the recommendation to screen for thyroid dysfunction (TD) during pregnancy. Although several studies have shown an association between maternal subclinical hypothyroidism and/or hypothyroxinemia with obstetric problems and/or neurocognitive impairment in the offspring, there is only limited evidence on the possible positive effects of thyroxine (T4) treatment in such cases. Despite the scarcity of this evidence, there is a widespread agreement among clinicians on the need for treatment of clinical hypothyroidism during pregnancy and the risks that could arise due to therapeutic abstention. As maternal TD is a quite prevalent condition, easily diagnosed and for which an effective and safe treatment is available, some scientific societies have proposed to assess thyroid function during the first trimester of pregnancy and ideally before week 10 of gestational age. Given the physiologic changes of thyroid function during pregnancy, hormone assessment should be performed using trimester-specific reference values ideally based on locally generated data as geographic variations have been detected. Screening of TD should be based on an initial determination of TSH performed early during the first trimester and only if abnormal should it be followed by either a free or total T4 measurement. Furthermore, adequate iodine supplementation during pregnancy is critical and if feasible it should be initiated before the woman attempts to conceive.

Hypothyroidism in pregnancy

Hypothyroidism is the most common pregnancy-related thyroid disorder, affecting 3-5% of all pregnant women. Subclinical hypothyroidism is more common than is overt hypothyroidism, and is usually defined as a serum thyroid-stimulating hormone (TSH) concentration greater than the pregnancy-specific reference range for each laboratory value, or by serum TSH concentrations greater than 2·5 mIU/L in the first trimester and greater than 3 mIU/L in the second and third trimesters. Some authors have defined subclinical hypothyroidism as a serum TSH between 5 and 10 mIU/L, and overt hypothyroidism as a serum TSH greater than 10 mIU/L, but this is not the commonly accepted definition. Once overt hypothyroidism is diagnosed, treatment with levothyroxine should be started to achieve serum TSH concentrations within the reference ranges for pregnancy as soon as possible. For patients with subclinical hypothyroidism, recommendations for therapy differ between various professional groups as a result of inconsistent data from both observational studies and clinical trials regarding the benefits for the mother or the child. Similarly, because benefits of therapy are still uncertain, universal screening of all pregnant women for subclinical hypothyroidism or thyroid autoimmunity is not recommended by most professional groups. During gestation, an increase in levothyroxine dose is required in more than 50% of women with previously diagnosed hypothyroidism, and can be managed by increasing the levothyroxine dose by 30% when pregnancy is confirmed.