Subclinical hypothyroidism in pregnancy: intellectual development of offspring

Subclinical hypothyroidism in the infertile female population: a guideline

There is controversy regarding whether to treat subtle abnormalities of thyroid function in infertile female patients. This guideline document reviews the risks and benefits of treating subclinical hypothyroidism in female patients with a history of infertility and miscarriage, as well as obstetric and neonatal outcomes in this population.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Maternal subclinical hyperthyroidism and adverse pregnancy outcomes considering the iodine status: Tehran thyroid and pregnancy study

BACKGROUND

Unlike overt thyroid diseases, the impacts of subclinical thyroid dysfunction, especially subclinical hyperthyroidism (SH), on adverse pregnancy outcomes are inconclusive.

OBJECTIVE

We aimed to investigate the effect of maternal SH on adverse maternal and neonatal outcomes based on urinary iodine concentration (UIC).

METHODS

A secondary analysis was run on data collected in the Tehran Thyroid and Pregnancy study (TTPs). We used the data of 131 women with SH and 1650 cases of euthyroid. Serum levels of thyroid-stimulating hormone (TSH), thyroxine (T4), free thyroxine index (FT4I), and thyroid peroxidase antibody (TPOAb) were assessed at the first prenatal visit. A generalized linear regression model was applied to identify the effect of SH on the pregnancy outcomes based on UIC, and the effects were estimated with a 95% confidence interval.

RESULTS

Preterm delivery was observed in 12.3% of women with SH and 6.7% of those with euthyroid (P = 0.03). Women with TSH< 0.3 mIU/L had a higher odds of preterm delivery than those with TSH≥ 0.3 regardless of urine iodine cut-off [OR= 2.27; 95% CI: (1.15, 4.48), p = 0.02]. Among those with UIC levels≥ 150 μg/L, the odds ratio of preterm delivery was 4.61 folds higher in the SH group compared to those with euthyroid [95%CI: (1.36, 15.71), p = 0.01)]. No significant difference between these two study groups was found in Neonatal Intensive Care Unit admission. Moreover, the results revealed no statistically significant difference in the means of neonatal anthropometric parameters in the SH and euthyroid groups in none of the subgroups of UIC (<150 or ≥150 µg/l).

CONCLUSIONS

According to our results, maternal SH appears to be a risk factor for preterm delivery. This effect is more pronounced in women with higher UIC than those with lower UIC.

Maternal Subclinical Hyperthyroidism and Adverse Pregnancy Outcomes: A Systematic Review and Meta-analysis of Observational Studies

CONTEXT

Findings from studies evaluating adverse pregnancy outcomes in pregnant women with subclinical hyperthyroidism are conflicting and inconclusive.

OBJECTIVES

In this systematic review and meta-analysis, our aim was to evaluate the pooled odds ratio (OR) of adverse pregnancy outcomes in women with subclinical hyperthyroidism, compared to euthyroid women.

DATA SOURCES

Scopus, PubMed (including Medline), and Web of Science databases were systemically searched for regaining published studies to January 2022 examining adverse pregnancy outcomes in women with subclinical hyperthyroidism.

STUDY SELECTION

Outcomes of interest were classified into seven composite outcomes, including hypertensive disorders, preterm delivery, macrosomia/large for gestational age (LGA), pregnancy loss, adverse maternal outcomes, adverse neonatal outcomes, and adverse fetal outcomes.

DATA EXTRACTION

In this meta-analysis, both fixed and random effect models were used. Publication bias was also evaluated by Egger test and the funnel plot, and the trim and fill method was conducted in case of a significant result, to adjust the bias.

RESULTS

Of 202 records retrieved through searching databases, 11 studies were selected for the final analyses. There were no significant differences in pooled ORs of hypertensive disorders, preterm delivery, macrosomia/LGA, and pregnancy loss in pregnant women with subclinical hyperthyroidism, compared to the euthyroid controls. The pooled OR of adverse maternal, neonatal, and fetal outcomes in pregnant women with subclinical hyperthyroidism was not statistically significantly different from that of the euthyroid control group.

CONCLUSIONS

The current meta-analysis demonstrated that subclinical hyperthyroidism in pregnancy is not related with adverse maternal and fetal outcomes. Therefore, clinicians should be avoided unnecessary treatments for pregnant women with subclinical hyperthyroidism.

Subclinical Hypothyroidism with Negative for Thyroid Peroxidase Antibodies in Pregnancy: Intellectual Development of Offspring

Background: The adverse impact of maternal negative TPOAb of gestational subclinical hypothyroidism (SCH-TPOAb^-) on the development of the offspring has not yet been clearly identified. A lingering controversy exists over the treatment of SCH-TPOAb^- diagnosed during pregnancy. Therefore, this study was designed to evaluate the intellectual development of children of mothers who had SCH-TPOAb^-. Methods: A number of 139 children were recruited; 112 children were born to SCH TPOAb^- and 27 children were born to euthyroid TPOAb^- mothers. Based on the mothers' thyrotropin (TSH) levels during pregnancy and whether or not they received levothyroxine (LT4) treatment, the children were assigned to four groups: Group A (2.5 mIU/L < TSH ≤4.0 mIU/L, n = 31) and Group B (4.0 mIU/L < TSH ≤10.0 mIU/L, n = 26), whose mothers were treated with LT4 before eight gestational weeks, and Group C (2.5 mIU/L < TSH ≤4.0 mIU/L, n = 27) and Group D (4.0 mIU/L < TSH ≤10.0 mIU/L, n = 28), whose mothers received no treatment. A total number of 27 children whose mother's serum TSH was <2.5 mIU/L and were TPOAb^- during their pregnancy served as the control group (Group E). The intellectual development of two-year-old children was assessed and compared using the Gesell Development Diagnosis Scale. Results: The developmental quotient (DQ) in Group D was 8.67 lower than this in Group E (p < 0.001). More specifically, gross motor quotient, fine motor quotient, adaptability quotient (ABQ), language quotient (LQ), and individual social behavior quotient (ISBQ) of DQ in Group D were significantly lower than those in Group E. No significant differences were observed in DQ among Group A, Group B, Group C, and Group E (p > 0.05). Spearman's rank correlation analysis showed that DQ, FMQ, ABQ, LQ, and ISBQ were significantly negatively correlated with the TSH level (r = -0.417, -0.253, -0.273, -0.436, and -0.272; p < 0.05). In addition, multivariate logistic regression analysis revealed that mothers' education (short education), mothers' education (medium education), and TSH level (4.0 mIU/L < TSH ≤10.0 mIU/L) were both risk factors affecting the intellectual development of the offspring (p < 0.05). Conclusion: The effects of the intellectual development of the offspring with SCH-TPOAb^- are related to the level of TSH. Standardized treatment for SCH-TPOAb^- pregnant women before eight gestational weeks, whose TSH level was from 4.0 to 10.0 mIU/L, may significantly improve the intellectual development levels of the approximately two-year-old offspring. Although our study was a historical cohort study, the data analyzed provide the foundation for further investigation. Further prospective intervention trials with large numbers of participants are needed to confirm our conclusions. The Clinical Trial Registration number is 2021-K-84-02.

Short-Term Adverse Pregnancy Outcomes in Women with Subclinical Hypothyroidism: A Comparative Approach of Iranian and American Guidelines

Introduction

Subclinical hypothyroidism during pregnancy can be associated with numerous adverse outcomes. The purpose of this study was to compare short-term adverse pregnancy outcomes in treated versus nontreated patients who fall within the numerical range of thyroid-stimulating hormone (TSH) between the Iranian and American reference ranges.

Materials and Methods

Eighty pregnant women with a known level of antithyroid peroxidase (anti-TPO) and TSH levels of 2.5–3.9 mIu/L in the first trimester and 3–4.1 mIu/L in the second and third trimesters were enrolled in the study and randomly assigned into two groups including 41 patients in the intervention group and 39 in the control group. The intervention group was treated with levothyroxine at least 50 μg/day and the control group received no treatment. The data were analyzed by SPSS software version 23.

Results

The only significant findings were a correlation between pregnancy loss frequency (p − 0.011) and/or increased TSH level in the follow-up period (p = 0.008) with anti-TPO antibody positivity. Forty-four percent of mothers with positive anti-TPO Ab needed treatment initiation with levothyroxine, based on Iranian guidelines, due to increased TSH level during the follow-up period.

Conclusion

Untreated pregnant women with subclinical hypothyroidism, who were placed in the intermediate range of TSH, recommended by Iranian and American guidelines, did not show any significant difference in short-term adverse pregnancy outcomes compared to the treated patients. Positive anti-TPO Ab may play a role in the development of short-term complications in mothers with subclinical hypothyroidism or it may increase the likelihood of an increase in TSH level during pregnancy.

The Study of Prevalence and Pattern of Thyroid Disorder in Pregnant Women: A Prospective Study

Background The most frequent thyroid disorder in pregnancy is maternal hypothyroidism. The geographical variation in the prevalence of hypothyroidism during pregnancy is very wide and ranges from 2.5% to 11%. The prevalence of hypothyroidism is more in Asian countries as compared to western countries. Thus, this study was conducted to find out the prevalence of thyroid disorder in pregnancy at our center. Methods The present study was conducted in the Department of Physiology in collaboration with the Department of Obstetrics & Gynecology, Index Medical College, Hospital and Research Center, Indore, MP, India over a period of one and a half years from October 2018 to March 2020. It was a cross-sectional study including 865 pregnant women. The patients' demographic profile was noted in all cases. A detailed history and thorough examination were done in all cases. Serum thyroid-stimulating hormone (TSH), Free T3, and Free T4 (FT3 and FT4) were done along with routine blood investigations as per The Federation of Obstetric and Gynaecological Societies of India-Indian College of Obstetricians and Gynaecologists (FOGSI-ICOG) good clinical practice recommendation. Results In this study, the prevalence of thyroid dysfunction was 10.4%. Of these 90 patients with thyroid dysfunction, subclinical and overt hypothyroidism was found in 5.50% and 0.92%, respectively, whereas subclinical and overt hyperthyroidism was observed in 3.12% and 0.81% pregnant females, respectively. A significant association was found between thyroid dysfunction and maternal age, BMI, parity, and education. Conclusions The prevalence of thyroid dysfunction was 10.4% in this study. Hypothyroidism was more common than hyperthyroidism and subclinical thyroid disorders were more common than overt thyroid disorders in pregnancy. Therefore, we should include thyroid function tests with other routine investigations during pregnancy to detect thyroid dysfunction.

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

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

Effects of thyroid diseases on pregnancy outcomes

The current study aimed to analyze the effects of thyroid diseases on pregnancy outcomes and investigate the effects of levothyroxine (L-T4) tablets in the treatment of hypothyroidism. The current study determined the prevalence of thyroid diseases using two diagnostic criteria, the prevalence of thyroid diseases among pregnant women recruited in 2010 and 2014 were initially determined by the 2011 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and Postpartum (2011 ATA Guidelines). Subjects were categorized into six groups: Normal, hypothyroxinemia, hypothyroidism, subclinical hypothyroidism (SCH), hyperthyroidism and subclinical hyperthyroidism. L-T4 was administered in the thyroid-insufficient groups and the prevalence rates of these categories were obtained using the diagnostic criteria from the 2011 ATA Guidelines and the 2012 Chinese Guidelines for the Diagnosis and Treatment of Thyroid Disease During Pregnancy and Postpartum (2012 Chinese Guidelines). The results of the current study demonstrated that the screening of thyroid function was significantly increased in 2014 (thyroid dysfunction rate, 82.4% vs. 29.1%; P<0.001). Hypothyroxinemia, hypothyroidism, SCH, hyperthyroidism and subclinical hyperthyroidism increased the likelihood of certain adverse outcomes and complications. L-T4 decreased the odds of gestational hypertension, premature birth and low birth weight or very low birth weight in the hypothyroidism group. A statistically significant difference was identified between thyroid disease incidences as determined by the 2011 ATA Guidelines 2012 Chinese Guidelines. In conclusion, abnormal thyroid levels increased the odds of adverse pregnancy outcomes, L-T4 administration improved pregnancy outcomes and the 2012 Chinese Guidelines may provide a better reference for Chinese pregnant women with subclinical hyperthyroidism.

Evaluation of the impact of levothyroxine treatment on the psychomotor developmental status of three-year-old children born to mothers with mild thyroid impairment; Tehran Thyroid and pregnancy study: study protocol for a randomized clinical trial

Background

Despite the known adverse effects of maternal overt hypothyroidism on the neurocognitive development of children, there is uncertainty regarding the impact of gestational thyroid dysfunction or autoimmune thyroiditis on infant/child neurological development. This study aims to evaluate the impact of levothyroxine (LT4) treatment on the psychomotor developmental status of three-year-old children born to mothers with mild thyroid impairment (subclinical hypothyroidismwith/without autoimmune thyroiditis).

Methods/Design

This is a follow-up study of the Tehran Thyroid and Pregnancy Study, a randomized trial in which subclinical hypothyroid pregnant women were assigned to an intervention group (treated with levothyroxine) or a control group (received no treatment). The primary outcome for the purpose of the present study is the developmental status of the children, aged three years, in five domains (communication, gross motor, fine motor, problem-solving, and social–personal domains) using the Ages and Stages Questionnaire (ASQ).

Discussion

The study is designed to assess the developmental status of children born to mothers with mild thyroid impairment (subclinical hypothyroidism with/without autoimmune thyroiditis). This study is one of the limited studies available in this field and has the potential to facilitate much-needed information for related public health policies.

Trial registration

Iranian Registry of Clinical Trials, IRCT2017090314849N5. Registered on 11 September 2017. Iranian Registry of Clinical Trials, IRCT2017090414849N6. Registered on 14 October 2017.

Electronic supplementary material

The online version of this article (10.1186/s13063-018-3130-5) contains supplementary material, which is available to authorized users.

Thyroid function and thyroid disorders during pregnancy: a review and care pathway

PURPOSE

To review the literature on thyroid function and thyroid disorders during pregnancy.

METHODS

A detailed literature research on MEDLINE, Cochrane library, EMBASE, NLH, ClinicalTrials.gov, and Google Scholar databases was done up to January 2018 with restriction to English language about articles regarding thyroid diseases and pregnancy.

RESULTS

Thyroid hormone deficiencies are known to be detrimental for the development of the fetus. In particular, the function of the central nervous system might be impaired, causing low intelligence quotient, and mental retardation. Overt and subclinical dysfunctions of the thyroid disease should be treated appropriately in pregnancy, aiming to maintain euthyroidism. Thyroxine (T4) replacement therapy should reduce thyrotropin (TSH) concentration to the recently suggested fixed upper limits of 2.5 mU/l (first and second trimester) and 3.0 mU/l (third trimester). Overt hyperthyroidism during pregnancy is relatively uncommon but needs prompt treatment due to the increased risk of preterm delivery, congenital malformations, and fetal death. The use of antithyroid drug (methimazole, propylthiouracil, carbimazole) is the first choice for treating overt hyperthyroidism, although they are not free of side effects. Subclinical hyperthyroidism tends to be asymptomatic and no pharmacological treatment is usually needed. Gestational transient hyperthyroidism is a self-limited non-autoimmune form of hyperthyroidism with negative antibody against TSH receptors, that is related to hCG-induced thyroid hormone secretion. The vast majority of these patients does not require antithyroid therapy, although administration of low doses of β-blocker may by useful in very symptomatic patients.

CONCLUSIONS

Normal maternal thyroid function is essential in pregnancy to avoid adverse maternal and fetal outcomes.

Validation of Billewicz Scoring System for Detection of Overt Hypothyroidism During Pregnancy

BACKGROUND

Currently, various clinical and laboratory diagnostic methods are used to detect overt hypothyroidism during pregnancy. The Billewicz scoring index, as a clinical scale for detection of hypothyroidism, has been applied in general populations; however, its application during pregnancy remains a controversial subject of ongoing research.

OBJECTIVES

The purpose of this study was to evaluate the diagnostic value of Billewicz scoring index for overt hypothyroidism in a general population of Iranian pregnant women.

METHODS

This study was conducted on 1843 pregnant women. A comprehensive questionnaire, including Billewicz scoring items, was completed, and relevant clinical examinations were performed. The participants underwent serum measurements of thyroxine (T4), thyroid hormone uptake, thyroid-stimulating hormone (TSH), and thyroid peroxidase antibody (TPOAb). Using the receiver operating characteristic (ROC) curve analysis, the optimal sensitivity and specificity were determined as values with maximum yields on the Youden and Rsquo's Index (sensitivity + specificity-1).

RESULTS

The prevalence of overt hypothyroidism and subclinical hypothyroidism was 3.3% and 28.6%, respectively. Overall, 3.6%, 18.9%, and 50% of euthyroid, subclinical hypothyroid, and overt hypothyroid women were TPOAb-positive, respectively. The mean Billewicz scores of euthyroid, overt hypothyroid, and subclinical hypothyroid women were -41.16 (11.16), -17.11 (13.63), and -40.1 (11.2), respectively. Based on the Billewicz scale, at least one sign of hypothyroidism was reported in 38.84% (n, 491) of euthyroid women. Scores ≤ -26.5 (sensitivity, 100%; specificity, 90.82%) were considered as the optimal scores for predicting overt hypothyroidism (Ldquo, Norisk, and Rsquo).

CONCLUSIONS

The Billewicz clinical scoring system, as a reliable and inexpensive clinical tool, used along with laboratory measurements, can help screen overt hypothyroidism during pregnancy, primarily in low-resource settings.

Secondary and tertiary preventions of thyroid disease

INTRODUCTION

Secondary and tertiary preventions are concerned with the recognition of the disease process in a very early stage and delay in progression to complete disease and minimization of complications and the impact of illness.

METHODS

All articles related to secondary and tertiary prevention of thyroid diseases were reviewed. Using related key words, articles published between 2001 and 2015 were evaluated, categorized, and analyzed.

RESULTS

In secondary prevention, congenital hypothyroidism and subclinical hypo and hyperthyroidism are equally important. Routine screening of patients with multinodular goiter by either ultrasonography or calcitonin is a controversial issue, while calcitonin assessments in medullary cancer and RET in family members are recommended. Screening of thyroid disease in pregnancy is limited to those with risk factors. Views regarding the importance of thyroid autoimmunity in secondary prevention are also presented. In tertiary prevention, prescribing excessive doses of levothyroxine, in the elderly in particular and appropriate care of all patients to avoid progression and complications are the key issues.

CONCLUSION

Optimization of management of thyroid diseases requires timely screening, prevention of progression to more sever disease, optimal medical care, and avoidance of iatrogenic conditions.

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

BACKGROUND

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

AIM

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

METHODS

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

RESULTS

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

LIMITATIONS

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

CONCLUSION

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

Identifying and treating subclinical thyroid dysfunction in pregnancy: emerging controversies

Thyroid hormones are essential for an adequate growth and development of the fetus. In addition to the classical association between maternal hypothyroidism and neurological impairment in the progeny, other adverse reproductive events have been associated with maternal thyroid dysfunction including infertility, miscarriage and preterm delivery. Although all scientific societies endorse the treatment of overt hypothyroidism; the management and/or treatment of subclinical hypothyroidism, hypothyroxinemia or antithyroid antibody-positive women should be considered with caution. Important trials have found no clear benefit of treatment of subclinical hypothyroidism in terms of cognitive outcomes; however, other interventional studies appear to reduce some of the obstetric and perinatal complications. As a result, the dilemma between universal screening or selective screening of women at high risk of thyroid dysfunction during pregnancy remains unresolved. Despite this, levothyroxine is also now regularly prescribed by gynaecologists and centres for reproductive medicine. In this context, there is increasing concern regarding the risk of over diagnosis and subsequent potential overtreatment. Taken together, we need to reconsider how thyroid dysfunction should be identified in pregnant women and highlight the arguments for and against the use of levothyroxine in obstetric practices. Our main findings: the mismatch between the guidelines recommendations and the use of LT4 in clinical settings as well as the disparity of criteria between scientific societies from different medical specialties. In conclusion, it is essential to reach agreements between both endocrinologists and obstetricians.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Benign thyroid disease in pregnancy: A state of the art review

Thyroid dysfunction is the commonest endocrine disorder in pregnancy apart from diabetes. Thyroid hormones are essential for fetal brain development in the embryonic phase. Maternal thyroid dysfunction during pregnancy may have significant adverse maternal and fetal outcomes such as preterm delivery, preeclampsia, miscarriage and low birth weight. In this review we discuss the effect of thyroid disease on pregnancy and the current evidence on the management of different thyroid conditions in pregnancy and postpartum to improve fetal and neonatal outcomes, with special reference to existing guidelines on the topic which we dissect, critique and compare with each other. Overt hypothyroidism and hyperthyroidism should be treated appropriately in pregnancy, aiming to maintain euthyroidism. Subclinical hypothyroidism is often pragmatically treated with levothyroxine, although it has not been definitively proven whether this alters maternal or fetal outcomes. Subclinical hyperthyroidism does not usually require treatment and the possibility of non-thyroidal illness or gestational thyrotoxicosis should be considered. Autoimmune thyroid diseases tend to improve during pregnancy but commonly flare-up or emerge in the post-partum period. Accordingly, thyroid auto-antibodies tend to decrease with pregnancy progression. Postpartum thyroiditis should be managed based on the clinical symptoms rather than abnormal biochemical results.

Update on the Management of Thyroid Disease during Pregnancy

Thyroid dysfunction during pregnancy can result in serious complications for both the mother and infant; however, these complications can be prevented by optimal treatment of maternal overt thyroid dysfunction. Although several studies have demonstrated that maternal subclinical hypothyroidism is associated with obstetric complications and neurocognitive impairments in offspring, there is limited evidence that levothyroxine treatment can improve these complications. Therefore, most professional societies do not recommend universal screening for thyroid dysfunction during pregnancy, and instead recommend a case-finding approach in which only high-risk women are tested. However, recent studies have estimated that targeted thyroid function testing misses approximately 30% to 55% of hypothyroidism cases in pregnant women, and some associations and researchers have recommended universal screening of pregnant women to facilitate the early detection and treatment of overt hypothyroidism. This review summarizes recent data on thyroid function test changes, thyroid functional disorder management, and thyroid screening during pregnancy.

Levothyroxine treatment of mild subclinical hypothyroidism: a review of potential risks and benefits

Subclinical hypothyroidism (SCH) is defined as elevated thyroid stimulating hormone (TSH) with normal levels of free triiodothyronine (FT3) and free thyroxine (FT4). SCH is further classified into a milder condition with TSH levels between 4.0 and 10.0 milli-international units (mIU)/l (mild-SCH) and a severe form with TSH >10.0 mIU/l (severe-SCH). SCH is a common problem (prevalence is greater in women than men), which increases further with increasing age and TSH levels. Even though the risk of progression to overt hypothyroidism is higher in patients with severe-SCH, the risk is also significant in patients having mild-SCH; it has been suggested that every twofold rise in serum TSH would increase the risk from 1 to 4%, which further increases to 38% if thyroid antibodies are positive. Current data have shown increased cardiovascular risk in patients with mild-SCH and have demonstrated some benefits of levothyroxine treatment in reducing these events. However, evidence on the association of mild-SCH and musculoskeletal system, cognitive dysfunction, mood disorders, dyslipidaemia, diabetes and goitre is conflicting. Similarly, the discussion regarding the exact upper limit of normal for serum TSH remains controversial. The data have also shown increased risk of adverse pregnancy outcomes in patient with mild-SCH, with some benefits of thyroxine treatment. The recent available guidelines related to management of patients with serum TSH <10 mIU/l have suggested decisions should be made taking into account the age of the patient, associated risk factors and comorbid conditions. This chronicle review assesses current evidence regarding the risks associated and the recommendations related to benefits of levothyroxine treatment in patients having mild-SCH.

Effects of Maternal Iodine Nutrition and Thyroid Status on Cognitive Development in Offspring: A Pilot Study

BACKGROUND AND OBJECTIVE

Maternal iodine nutrition and thyroid status may influence neurocognitive development in offspring. This study investigated the effects on the intelligence quotient (IQ) of children born to mothers with different levels of iodine supplementation, with or without the administration of levothyroxine (LT4), prior to and during pregnancy.

PATIENTS AND METHODS

This pilot, prospective, observational study included four study groups, each comprising 15 mother-child pairs, identified on the basis of maternal histories of iodized salt consumption and LT4 treatment prior to and during pregnancy. The groups were labeled as follows: iodine (I), no iodine (no-I), iodine + LT4 (I + T4), and no iodine + LT4 (no-I + T4). IQ tests were administered to children at 6-12 years of age with the Wechsler Intelligence Scale for Children-3rd Edition (WISC-III), with full-scale IQ (FSIQ), verbal IQ (VIQ), and performance IQ (PIQ) being evaluated.

RESULTS

Children of I and I + T4 mothers had similar verbal, performance, and FSIQs, which were 14, 10, and 13 points higher, respectively, than children born to no-I and no-I + T4 mothers. A positive association was found between VIQ and maternal urinary iodine (β = 1.023 [confidence interval (CI) 1.003-1.043]; p = 0.028), but not with maternal free thyroxine concentrations at any stage of pregnancy. Overall, the prevalence of borderline or defective cognitive function was more than threefold higher in the children of mothers not using iodized salt than of those mothers using it (76.9% vs. 23.1%, odds ratio 7.667 [CI 2.365-24.856], χ2 = 12.65; p = 0.0001).

CONCLUSIONS

Neuro-intellectual outcomes in children appear to be more dependent on their mothers' nutritional iodine status than on maternal thyroid function. These results support the growing body of evidence that prenatal, mild-to-moderate iodine deficiency adversely affects cognitive development later in life, with a seemingly greater impact on verbal abilities.

Comparison of universal screening with targeted high-risk case finding for diagnosis of thyroid disorders

OBJECTIVE

Debate about the need for universal screening of thyroid dysfunction in pregnancy is ongoing. The present study aimed to compare universal screening with targeted high-risk case findings for early diagnosis of thyroid disorders in Iranian pregnant women.

STUDY DESIGN

This cross-sectional prospective study was carried out on 1600 pregnant women in their first trimester. A checklist, including all related risk factors recommended by The American Thyroid Association, was completed for all participants. Serum concentrations of thyroxine (T4), T-uptake, TSH and thyroid peroxidase antibody (TPOAb) were measured and thyroid status was documented, based on hormonal measurements and clinical examinations.

RESULTS

There were 656 women (44.3%) that had at least one risk factor for thyroid diseases and were eligible for the targeted high-risk case finding (high-risk group) approach, while 55.7% had no risk factors (low-risk group). Using the universal screening approach, there were 974 women (65.8%) with normal thyroid status and 506 participants (34.2%) with thyroid disturbances, including overt hyperthyroidism (0.7%), overt hypothyroidism (1.1%), subclinical hypothyroidism (30.1%; positive TPOAb (5.5%) and negative TPOAb (24.6%); and euthyroid and positive TPOAb (2.3%). Of women with thyroid dysfunction, 64.4% were in the high-risk group and 35.6% were in the low-risk group (P<0.0001).

CONCLUSIONS

The targeted high-risk case finding approach overlooks about one-third of pregnant women with thyroid dysfunction. If ongoing prospective trials provide evidence on the efficacy of treating subclinical hypothyroidism in pregnancy, in populations with a low prevalence of presumed risk factors, the targeted high-risk case finding approach will be proven inefficient.

Association between the clinical classification of hypothyroidism and reduced TSH in LT4 supplemental replacement treatment for pregnancy in China

The study was aimed to evaluate the effects of levothyroxine (LT4) supplemental replacement treatment for pregnancy and analyze the associations between the clinical classification of hypothyroidism and reduced thyroid-stimulating hormone (TSH) in LT4 therapy. Totally, 195 pregnant women with hypothyroidism receiving routine prenatal care were enrolled. They were categorized into three groups: overt hypothyroidism (OH), subclinical hypothyroidism (SCH) with negative thyroperoxidase antibody (TPOAb), and SCH with positive TPOAb. The association between the clinical classification and reduced TSH in LT4 supplemental replacement treatment was assessed. The results indicated that reduced TSH was significantly different among the groups according to the clinical classifications (p = 0.043). The result was also significantly different between patients with OH and patients with SCH and negative TPOAb (p = 0.036). Similar result was reported for the comparison between patients with OH and patients with SCH and positive TPOAb (p = 0.016). Multiple variable analyses showed that LT4 supplementation, gestational age and the variable of clinical classifications were associated with reduced TSH independently. Our data suggested that the therapeutic effect of substitutive treatment with LT4 was significantly associated with different clinical classifications of hypothyroidism in pregnancy and the treatment should begin as soon as possible after diagnosis.

Effect of gestational subclinical hypothyroidism on early neurodevelopment of offspring

OBJECTIVE

To evaluate the effects of gestational subclinical hypothyroidism (SCH) on early neurodevelopment of offspring.

STUDY DESIGN

A prospective study included 106 infants born to mothers with gestational SCH and 106 infants born to mothers who were euthyroid during pregnancy. The neurodevelopment of 12 to 24-month-old infants was assessed and compared using the Gesell developmental test (revised version).

RESULTS

Infants born to mothers with gestational SCH and those born to euthyroid mothers had similar scores on the Gesell development test. No correlations were observed between maternal TSH concentration and Gesell developmental test scores of offspring. Infants born to mothers who had gestational SCH during the first trimester specifically and those born to euthyroid mothers had similar scores on the Gesell development test. No significant correlations were detected between maternal TSH concentration during the first trimester and offspring neurodevelopment.

CONCLUSIONS

No detectable neurodevelopment deficit was observed in offspring up to 24 months old from mothers who had gestational SCH.

The importance of iodine in public health

Iodine (I) deficiency has been known for more than a century and is known to cause cretinism at the extreme end of the spectrum but also, importantly, impaired development and neurocognition in areas of mild deficiency. The WHO has indicated that median urinary iodine of 100-199 μg/l in a population is regarded as indicative of an adequate iodine intake. The understanding of the spectrum of iodine deficiency disorders led to the formation of The International Council for the Control of Iodine Deficiency Disorders which has promulgated the use of household iodized salt and the use of such salt in food processing and manufacture. Iodine deficiency is particularly important in pregnancy as the fetus relies on maternal thyroxine (T4) exclusively during the first 14 weeks and also throughout gestation. As this hormone is critical to brain and nervous system maturation, low maternal T4 results in low child intelligence quotient. The recommendation for I intake in pregnancy is 250 μg/day to prevent fetal and child brain function impairment. During the past 25 years, the number of countries with I deficiency has reduced to 32; these still include many European developed countries. Sustainability of adequate iodine status must be achieved by continuous monitoring and where this has not been performed I deficiency has often recurred. More randomized controlled trials of iodine supplementation in pregnancy are required in mild iodine-deficient areas to inform public health strategy and subsequent government action on suitable provision of iodine to the population at risk.

Thyroid dysfunction and pregnancy outcomes

BACKGROUND

Pregnancy has a huge impact on the thyroid function in both healthy women and those that have thyroid dysfunction. The prevalence of thyroid dysfunction in pregnant women is relatively high.

OBJECTIVE

The objective of this review was to increase awareness and to provide a review on adverse effect of thyroid dysfunction including hyperthyroidism, hypothyroidism and thyroid autoimmune positivity on pregnancy outcomes.

MATERIALS AND METHODS

In this review, Medline, Embase and the Cochrane Library were searched with appropriate keywords for relevant English manuscript. We used a variety of studies, including randomized clinical trials, cohort (prospective and retrospective), case-control and case reports. Those studies on thyroid disorders among non-pregnant women and articles without adequate quality were excluded.

RESULTS

Overt hyperthyroidism and hypothyroidism has several adverse effects on pregnancy outcomes. Overt hyperthyroidism was associated with miscarriage, stillbirth, preterm delivery, intrauterine growth retardation, low birth weight, preeclampsia and fetal thyroid dysfunction. Overt hypothyroidism was associated with abortion, anemia, pregnancy-induced hypertension, preeclampsia, placental abruption, postpartum hemorrhage, premature birth, low birth weight, intrauterine fetal death, increased neonatal respiratory distress and infant neuro developmental dysfunction. However the adverse effect of subclinical hypothyroidism, and thyroid antibody positivity on pregnancy outcomes was not clear. While some studies demonstrated higher chance of placental abruption, preterm birth, miscarriage, gestational hypertension, fetal distress, severe preeclampsia and neonatal distress and diabetes in pregnant women with subclinical hypothyroidism or thyroid autoimmunity; the other ones have not reported these adverse effects.

CONCLUSION

While the impacts of overt thyroid dysfunction on feto-maternal morbidities have been clearly identified and its long term impact on childhood development is well known, data on the early and late complications of subclinical thyroid dysfunction during pregnancy or thyroid autoimmunity are controversial. Further studies on maternal and neonatal outcomes of subclinical thyroid dysfunction maternal are needed.

Optimal management of hypothyroidism, hypothyroxinaemia and euthyroid TPO antibody positivity preconception and in pregnancy

Normal physiological changes of pregnancy warrant the need to employ gestation specific reference ranges for the interpretation of thyroid function tests. Thyroid hormones play crucial roles in foetal growth and neurodevelopment which are dependent on adequate supply of maternal thyroid hormones from early gestation onwards. The prevention of significant adverse obstetric and neurodevelopmental outcomes from hypothyroidism requires a strategy of empirical levothyroxine dose increases and predictive dose adjustments in pregnancy combined with regular thyroid function testing, starting before pregnancy and until the postpartum period. Subclinical hypothyroidism has been associated with an increased risk of pregnancy loss and neurocognitive deficits in children, especially when diagnosed before or during early pregnancy. Whilst trials of levothyroxine replacement for mild hypothyroidism in pregnancy have not indicated definite evidence of improvements in these outcomes, professional guidelines recommend treatment, especially if evidence of underlying thyroid autoimmunity is present. Studies of isolated hypothyroxinaemia in pregnancy have shown conflicting evidence with regards to adverse obstetric and neurodevelopmental outcomes and no causative relationships have been determined. Treatment of this condition in pregnancy may be considered in those with underlying thyroid autoimmunity. Whilst the evidence for a link between the presence of anti-TPO antibodies and increased risks of pregnancy loss and infertility is compelling, the results of ongoing randomized trials of levothyroxine in euthyroid women with underlying autoimmunity are currently awaited. Further studies to define the selection of women who require levothyroxine replacement and to determine the benefits of a predictive dose adjustment strategy are required.

Reversible morbidity markers in subclinical hypothyroidism

IMPORTANCE

Subclinical hypothyroidism (SCH) is a common clinical entity with a putative role in a wide range of disorders. The impact of SCH on mortality and markers of morbidity has been demonstrated, but studies have shown inconsistent results. Evidence regarding the effect of levothyroxine treatment on reversing morbidity markers is emerging, but the value of treatment is still unclear.

OBJECTIVE

The objectives of this review were to assess recent, high-quality studies evaluating the role of SCH in cardiovascular health, cognition, mood, pregnancy, anemia, and renal disease; to examine the effects of levothyroxine on reducing mortality or reversing markers of morbidity in these conditions; and to consider how new research insights may help guide clinical practice.

EVIDENCE REVIEW

A PubMed search was conducted (using 'subclinical hypothyroidism' [Title/Abstract] AND morbidity [MeSH Subheading] as search criteria) and was restricted to human studies published in the English language between 1990 and 2013. Subsequent searches of retrieved articles yielded further studies, which were included based on quality. Emphasis was given to large observational studies, well-conducted meta-analyses, and randomized controlled trials.

FINDINGS

The difficulty of diagnosing SCH, particularly in the elderly, may underlie many of the conflicting results seen in the literature. Increased understanding of the at-risk patient population will result in better selection of study subjects and, likely, unequivocal results. Regardless of the current confusion, emerging evidence suggests that certain markers of morbidity are reversed by levothyroxine therapy across the disorders examined here.

CONCLUSION AND RELEVANCE

Future large, well-controlled studies will not only clarify the role of SCH but also help identify patients for whom levothyroxine treatment will provide the most benefit.

2014 European thyroid association guidelines for the management of subclinical hypothyroidism in pregnancy and in children

This guideline has been produced as the official statement of the European Thyroid Association guideline committee. Subclinical hypothyroidism (SCH) in pregnancy is defined as a thyroid-stimulating hormone (TSH) level above the pregnancy-related reference range with a normal serum thyroxine concentration. Isolated hypothyroxinaemia (defined as a thyroxine level below the 2.5th centile of the pregnancy-related reference range with a normal TSH level) is also recognized in pregnancy. In the majority of SCH the cause is autoimmune thyroiditis but may also be due to iodine deficiency. The cause of isolated hypothyroxinaemia is usually not apparent, but iodine deficiency may be a factor. SCH and isolated hypothyroxinaemia are both associated with adverse obstetric outcomes. Levothyroxine therapy may ameliorate some of these with SCH but not in isolated hypothyroxinaemia. SCH and isolated hypothyroxinaemia are both associated with neuro-intellectual impairment of the child, but there is no evidence that maternal levothyroxine therapy improves this outcome. Targeted antenatal screening for thyroid function will miss a substantial percentage of women with thyroid dysfunction. In children SCH (serum TSH concentration >5.5-10 mU/l) normalizes in >70% and persists in the majority of the remaining patients over the subsequent 5 years, but rarely worsens. There is a lack of studies examining the impact of SCH on the neuropsychological development of children under the age of 3 years. In older children, the evidence for an association between SCH and impaired neuropsychological development is inconsistent. Good quality studies examining the effect of treatment of SCH in children are lacking.

Thyroid disorders during pregnancy

Thyroid disorders are common in pregnancy and in nonpregnant women of childbearing age, but can be missed because of nonspecific symptoms and normal changes in thyroid gland physiology during pregnancy. The prevalence of overt hyperthyroidism complicating pregnancy has been reported to range between 0.4% and 1.7%, and an estimated 2% to 3% of women are hypothyroid during pregnancy. Abnormalities in maternal thyroid function are associated with complications during pregnancy, and may affect maternal and fetal outcomes. Thus it is important to identify thyroid disorders before pregnancy or early in pregnancy so that appropriate treatment can be initiated.

Pregnancy-induced alterations in mitochondrial function in euthyroid pregnant women and pregnant women with subclinical hypothyroidism; relation to adverse outcome

Background

It is well documented that overt hypothyroidism is associated with adverse pregnancy outcomes, but studies of subclinical hypothyroidism have demonstrated conflicting results.

Objective

Thyroid hormones are known to regulate mitochondrial function, and the aim of this study was to examine the possible relationship of subclinical hypothyroidism and mitochondrial dysfunction to adverse pregnancy outcomes in pregnant women.

Methods

Women in their third trimester of pregnancy (n = 113) who did not receive thyroid medication were included in this cross-sectional study. All participants were interviewed, and their thyroid status was determined. All participants had concentrations of thyroid hormones (fT₄ and tT₃) within the reference range. In addition to thyroid status, mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) were measured by flow cytometry. To establish a reference range of MMP and ROS, a group of euthyroid, nonpregnant women were used as euthyroid controls. Adverse pregnancy outcome was defined as preterm delivery, preeclampsia, placental abruption, Apgar score <7 points 1 minute after birth, or postpartum hemorrhage.

Results

The prevalence of subclinical hypothyroidism among pregnant women was 17% (n = 19), and the number of overall adverse pregnancy outcomes was increased (p = 0.02) compared with that in euthyroid pregnant women. Preeclampsia, poor Apgar score, and postpartum hemorrhage were more frequent in the subclinical hypothyroidism group than in the euthyroid group (p = 0.04, p = 0.001 and p = 0.03, respectively), and more women showed prolonged gestation and gave birth later than 41 weeks of gestation than in the euthyroid group (p = 0.04). Compared with euthyroid, nonpregnant controls, a physiological upregulation of mitochondrial function was observed in euthyroid pregnant women. This was impaired in pregnant women with subclinical hypothyroidism. Compared with euthyroid, nonpregnant controls, pregnant women had increased ROS regardless of their thyroid status.

Conclusion

We speculate that the unfavorable effects on mitochondrial function in women with subclinical hypothyroidism may be associated with higher prevalence of adverse pregnancy outcomes.

Adequate levothyroxine doses for the treatment of hypothyroidism newly discovered during pregnancy

BACKGROUND

Recent guidelines recommend thyrotropin (TSH) target levels of ≤2.5 mIU/L for the first trimester and ≤3 mIU/L for the subsequent trimesters. Euthyroidism should be attained as soon as possible, but there are no precise indications about the initial levothyrorine (LT4) dose. The aim of our study was to determine the appropriate LT4 doses in order to normalize TSH levels in patients with newly discovered subclinical hypothyroidism (SCH) during pregnancy, and to correlate them with basal TSH levels. The adequate LT4 doses for women with SCH were also compared to those required in pregnant women with overt hypothyroidism (OH).

METHODS

Seventy-seven patients with newly diagnosed hypothyroidism during pregnancy were retrospectively analyzed. Patients were assigned to group 1 (n = 64) with SCH or group 2 (n = 13) with OH. SCH patients were subdivided into two groups: group 1a serum TSH >2.5 (1st trimester) or >3 (2nd or 3rd trimester) to 4.2 mIU/L; and group 1b TSH level > 4.21-10 mIU/L. All patients were treated with LT4 as soon as hypothyroidism was diagnosed. The dose that allowed a TSH of ≤2.5 mIU/L to be reached in the first trimester or one that allowed a TSH of ≤3 mIU/L to be reached during the second and third trimesters was considered the appropriate one.

RESULTS

A significant difference (p < 0.0001) in the appropriate LT4 dose (mean ± SD, μg/kg/day) was observed between group 1 and group 2: 1.31 ± 0.36 versus 2.33 ± 0.59. Patients in group 1a required a significantly lower LT4 dose (p < 0.014) than group1b: 1.20 ± 0.39 versus 1.42 ± 0.31 μg/kg/day. In 57 of the 64 (89.06%) women with SCH and in 10/13 (76.92%) women with OH, the appropriate LT4 dose coincided with the initial dose. Only 11% and 23% respectively required additional adjustments. Once the appropriate dose of LT4 was prescribed, the time at which euthyroidism (mean ± SD, weeks) was confirmed was similar in patients with SCH (6.06 ± 3.3) and OH (5.3 ± 1.8). There were no miscarriages or premature deliveries.

CONCLUSIONS

When hypothyroidism is newly discovered during pregnancy, we suggest initiating the treatment with the following LT4 doses: 1.20 μg/kg/day for SCH with TSH ≤ 4.2  mIU/L, 1.42 μg/kg/day with TSH > 4.2-10, and 2.33 μg/kg/day for OH. By taking this approach, patients will promptly attain the euthyroid state avoiding additional increments and, probably, obstetric risks.

Establishing trimester-specific maternal thyroid function reference intervals

Background

Thyroid disorders are common in women of childbearing age and are associated with adverse pregnancy outcomes. Physiological changes in pregnancy and the lack of pregnancy-specific reference ranges make managing thyroid disorders in pregnancy challenging. Our aim was to establish trimester-specific thyroid function reference intervals throughout pregnancy, and to examine the prevalence of thyroid autoimmunity in otherwise euthyroid women.

Method

This was a prospective, cross-sectional study of thyroid function tests (TFTs) in pregnant women attending a large, tertiary referral maternity hospital. Patients with known thyroid disorders, autoimmune disease, recurrent miscarriage, hyperemesis gravidarum and pre-eclampsia were excluded. TFTs were analysed in the CUH biochemistry laboratory using Roche Modular E170 electrochemiluminescent immunoassay. Trimester-specific reference ranges (2.5th, 50th and 97.5th centiles) were calculated.

Results

Three-hundred-and-fifty-one women were included into the analysis. Median maternal age was 30. Thyroid-stimulating hormone concentrations showed slightly increasing median centile throughout gestation. Free thyroxine (T4) and T3 decreased throughout gestation. Table 1 demonstrates the calculated percentiles according to gestational weeks.

Conclusion

We established pregnancy-specific thyroid function reference intervals for our pregnant population, for use in clinical practice.

Screening for overt thyroid disease in early pregnancy may be preferable to searching for small aberrations in thyroid function tests

Thyroid hormones are important regulators of foetal development, and in recent years, there has been much focus on the screening and treatment of pregnant women for even small aberrations in thyroid function tests. We searched PubMed for publications on thyroid function and pregnancy outcomes including child cognition, and included references from the retrieved articles. Both small aberrations in thyroid function tests in early pregnancy and an increase in risk of pregnancy complications may be caused by a functional change in the uteroplacental unit. Thus, the association found in several studies between small thyroid test abnormalities and pregnancy complications may be due to confounding, and thyroid hormone therapy will have no effect. On the other hand, screening of thyroid function in early pregnancy may identify 200-300 women with undiagnosed overt hypothyroidism per 100,000 pregnancies, which is at least five times more than the number of hypothyroid newborns identified by screening. A number of studies indicate that untreated overt thyroid disease in pregnancy may lead to complications. The potential benefit of screening and early therapy is supported by evidence, indicating that even severe maternal hypothyroidism does not lead to neurocognitive deficiencies in the child, if the condition is detected and treated during the first half of pregnancy. Screening and therapy for overt thyroid dysfunction in early pregnancy may be indicated, rather than focusing on identifying and treating small aberrations in thyroid function tests.

Treatment of thyroid disorders before conception and in early pregnancy: a systematic review

BACKGROUND

Thyroid disorders are associated with pregnancy complications. Universal screening is currently not recommended because of a lack of evidence on the effectiveness of treatment. Women with hyperthyroidism and hypothyroidism evidently require treatment but this is less clear for women with subclinical hypothyroidism and thyroid autoimmunity. Therefore, we conducted a systematic review to provide a comprehensive overview on the available treatment interventions.

METHODS

Relevant studies were identified by searching Medline, EMBASE and Cochrane Controlled Trials Register, published until December 2011.

RESULTS

From a total of 7334 primary selected titles, 22 articles were included for the systematic review and 11 were appropriate for meta-analyses. Eight studies reported on hyperthyroidism. Propylthiouracil (PTU) and methimazole reduce the risk for preterm delivery [risk ratio (RR): 0.23, confidence interval (CI): 0.1-0.52], pre-eclampsia (RR: 0.23, CI: 0.06-0.89) and low birthweight (RR: 0.38, CI: 0.22-0.66). The nine studies that reported on clinical hypothyroidism showed that levothyroxine is effective in reducing the risk for miscarriage (RR: 0.19, CI: 0.08-0.39) and preterm delivery (RR: 0.41, CI: 0.24-0.68). For treatment of subclinical hypothyroidism, current evidence is insufficient. The five studies available on thyroid autoimmunity showed a not significant reduction in miscarriage (RR: 0.58, CI: 0.32-1.06), but significant reduction in preterm birth by treatment with levothyoxine (RR: 0.31, CI: 0.11-0.90).

CONCLUSION

For hyperthyroidism, methimazole and PTU are effective in preventing pregnancy complications. For clinical hypothyroidism, treatment with levothyroxine is recommended. For subclinical hypothyroidism and thyroid autoimmunity, evidence is insufficient to recommend treatment with levothyroxine. The overall lack of evidence precludes a recommendation for universal screening and is only justified in a research setting.

Thyroid disorders during pregnancy

Thyroid disorders are common in women during pregnancy. If left untreated, both hypothyroidism and hyperthyroidism are associated with adverse effects on pregnancy and fetal outcomes. It is important to correctly identify these disorders and treat them appropriately to prevent pregnancy-related complications. Levothyroxine is the indicated treatment for hypothyroidism, and thionamides are the treatment of choice for hyperthyroidism; thyroidectomy may be indicated in select cases. When thyroid cancer is diagnosed during pregnancy, a decision must be made regarding performing thyroidectomy during the pregnancy or postponing surgical resection until the postpartum period. Radioactive iodine is absolutely contraindicated during pregnancy and lactation.