Drug therapy for hyperthyroidism in pregnancy: safety issues for mother and fetus

Maternal Thyroid Anomalies and Attention-Deficit Hyperactivity Disorder in Progeny

Previous epidemiologic investigations suggested that maternal thyroid anomalies are a possible causal factor in attention-deficit hyperactivity disorder (ADHD) in progeny, yet clinical trials indicated that levothyroxine treatment was ineffective in preventing neurodevelopmental impairments. We used an Israeli cohort of 385,542 singleton births from 1999-2012 to explore the interrelated roles of maternal thyroid conditions, laboratory gestational thyroid hormone measurements, use of thyroid medications, and offspring ADHD. Analyses were performed using Cox proportional hazards models. Results indicated that maternal hypothyroidism diagnosis was associated with an elevated progeny ADHD hazard (adjusted hazard ratio = 1.14, 95% confidence interval = 1.10, 1.18). However, this association was unmitigated by gestational use of levothyroxine and was unexplained by maternal gestational thyroid hormone levels. Associations with gestational thyrotropin values and hypothyroxinemia were also observed but were robust only in mothers without other records indicative of a thyroid problem. Results indicated that maternal thyroid hypofunction was associated with progeny ADHD but possibly not due to a direct causal relationship. Instead, maternal thyroid hypofunction may serve as a proxy indicator for other factors that affect neurodevelopment through thyroid hormone independent pathways, which are thus unaffected by pharmaceutical treatments for thyroid hypofunction. Factors known to disrupt thyroid functioning should be examined for their independent ADHD-related effects.

The Tired Pregnant Woman

Introduction

Many pregnant women develop hyperemesis gravidarum. There are numerous gastrointestinal, genitourinary, neurologic, and metabolic causes to consider in this patient population.

Case Presentation

This clinicopathological case presentation details the initial assessment and management of an 18-year-old pregnant patient who presented to the emergency department with a complaint of nausea, vomiting, fatigue, and intermittent bleeding.

Discussion

This case takes the reader through the differential diagnosis and evaluation of the patient and the signs and symptoms, including her agitation and tachycardia, that led us to the correct diagnosis.

Maternal Thyroid Disorders and Risk of Autism Spectrum Disorder in Progeny

BACKGROUND

Maternal thyroid dysfunction is suspected of causing adverse neurodevelopmental effects, but current evidence is inconclusive. Epidemiologic investigations generally suggest an association between maternal thyroid dysfunction and neurodevelopment impairments in progeny, but clinical trials of thyroid treatment during pregnancy reported null effects. To better understand these discrepant findings, we evaluated the association between maternal thyroid conditions and autism spectrum disorder (ASD), including examining the role of gestational thyroid-related hormone concentrations and thyroid medications use.

METHODS

Analyses considered 437,222 singleton live births occurring in a large Israeli health fund in 1999-2013, followed through 2016. Thyroid conditions and ASD cases were identified through International Classification of Diseases-9 codes with subsequent validation through review of medical records. Laboratory gestational thyroid hormone measurements were also considered.

RESULTS

Children of mothers who ever experienced hypothyroidism had a higher risk of ASD compared with children of mothers without hypothyroidism (adjusted odds ratio [aOR] = 1.26, 95% confidence interval [CI] = 1.12, 1.42). The association with hyperthyroidism was less consistent, but elevated in main analyses (aOR = 1.42, 95% CI = 1.04, 1.94). These associations were not explained by maternal gestational thyroid hormones levels nor mitigated by gestational use of thyroid medications.

CONCLUSIONS

Results indicate that maternal thyroid conditions are associated with increased ASD risk in progeny, but suggestively not due to direct effects of thyroid hormones. Instead, factors that influence maternal thyroid function could have etiologic roles in ASD through pathways independent of maternal gestational thyroid hormones and thus be unaffected by medication treatment. Factors known to disrupt thyroid function should be examined for possible involvement in ASD etiology.

Propylthiouracil, and methimazole, and carbimazole-related hepatotoxicity

INTRODUCTION

Propylthiouracil (PTU) has been used for the treatment of hyperthyroidism since the 1940s, but over the years reports of significant hepatotoxicity have come forth, particularly in children. This led to a black box warning being issued by the US FDA in 2009, followed by a similar warning by the European Medicines Agency and the United Kingdom Medicines and Healthcare Regulatory Agency later that year.

AREAS COVERED

This article provides a concise review of the data on hepatotoxicity associated with the currently available antithyroid drugs: PTU, methimazole (MMI) and carbimazole. The differences in mechanism are examined in detail, as well as clinical presentation, management and monitoring. Use in special populations and trends in use of antithyroid medication are also discussed.

EXPERT OPINION

PTU is known to cause severe hepatic failure, particularly in children. Its use in children should be avoided. In adults, it is beneficial to use in the first trimester of pregnancy and thyroid storm. In the rest of the adult population, it should be used with caution. Carbimazole and MMI are associated with less severe hepatic injury and should be preferred when choosing thionamides as a treatment option.

Maternal hyperthyroidism increases the prevalence of foregut atresias in fetal rats exposed to adriamycin

PURPOSE

Gastrointestinal malformations such as esophageal atresia with tracheoesophageal fistula (EA/TEF) and duodenal atresia (DA) have been reported in infants born to hyperthyroid mothers or with congenital hypothyroidism. The present study aimed to test whether maternal thyroid status during embryonic foregut division has any influence on the prevalence of EA/TEF and DA in an accepted rat model of these malformations.

METHODS

Pregnant rats received either vehicle or 1.75 mg/kg i.p. adriamycin on gestational days 7, 8 and 9. Transient maternal hyper or hypothyroidism was induced by oral administration of levothyroxine (LT4, 50 μg/kg/day) or propylthiouracil (PTU, 2 mg/kg/day), respectively, on days 7 to 12 of gestation. Plasma cholesterol, total T3, free T4 and TSH were measured at gestational days 7, 12, and 21. At the end of gestation, the mothers were sacrificed and embryo-fetal mortality was recorded. Fetuses were dissected to determine the prevalence of esophageal and intestinal atresias.

RESULTS

At gestational day 12, mothers treated with LT4 or PTU had hyper or hypothyroid status, respectively; plasma cholesterol levels were similar. In the adriamycin-exposed fetuses from hyperthyroid mothers, the embryonal resorption rate and the prevalence of both EA/TEF and DA were significantly higher than in the other groups; maternal hypothyroidism during the same period did not have significant effect on the prevalence of atresias.

CONCLUSIONS

Maternal hyperthyroidism during the embryonic window corresponding to foregut cleavage increased the prevalence of both EA/TEF and duodenal atresia in fetal rats exposed to adriamycin. This suggests that maternal thyroid hormone status might be involved in the pathogenesis of foregut atresias and invites further research on this likely clinically relevant issue in humans.

The effects of short-term manipulation of thyroid hormone status coinciding with primary wool follicle development on fleece characteristics in Merino sheep

Thyroidectomy surgery performed late in gestation results in perturbations in wool follicle development in foetal sheep, showing the importance of thyroid hormones for wool follicle development. The aim of this study was to determine the influence of transient manipulation of thyroid hormone status at a time corresponding with foetal primary wool follicle initiation. Pregnant Merino ewes (n = 12 per treatment) were treated daily between gestational days 55 and 64 with control (vehicle), exogenous thyroxine (T4) or propylthiouracil (PTU), an inhibitor of T4 synthesis, and conversion to the active form of the thyroid hormone (triiodothyronine). There were no significant differences in birth weight, gestational lengths and birth coat scores of the resultant lambs. The total primary and secondary follicle densities were significantly lower in lambs exposed to exogenous T4 compared with other treatments (P < 0.05). However, the T4 group displayed a higher proportion of mature secondary follicles (reflected by increased mature secondary follicle densities and mature secondary/primary follicle ratios) than the other treatment groups (P < 0.05). The skin morphology of the lambs differed 12 months later, with the T4 group having significantly higher total follicle densities compared with the PTU group, largely attributed to increased mature and total secondary follicle densities. However, this increase in wool follicle densities did not translate to differences in the fleece yields and weight, fibre diameter, staple lengths or any other fibre parameters. This study showed that transient manipulation of thyroid hormone status during foetal primary follicle initiation does have long-term consequences on the morphology of wool follicles, in particular the maturity of secondary wool follicles.

Thyroid function and 3,3'-diiodothyronine sulfate cross-reactive substance (compound W) in maternal hyperthyroidism with antithyroid treatment

OBJECTIVE

To test whether the serial measurement of maternal levels of compound W, a 3,3'-diiodothyronine sulfate cross-reactive substance, can serve as a potential indicator of fetal thyroid function in pregnant women receiving antithyroid medication.

METHODS

Compound W was measured repeatedly in serum of pregnant women with hyperthyroidism treated with antithyroid medication. Free thyroxine levels of mothers and serum thyroid-stimulating hormone levels of 1-day-old neonates were analyzed by local clinical or state laboratories.

RESULTS

Use of minimal antithyroid medication impaired the progressive increase of compound W seen in euthyroid mothers during pregnancy. At term, depressed compound W levels in maternal serum were found in 7 of 22 pregnancies; in 1 case, maternal compound W was suppressed and newborn thyroid-stimulating hormone was elevated. Seven mothers with treated hyperthyroidism failed to show an increase in serum levels of compound W after midterm.

CONCLUSION

Normal progression of maternal serum compound W may be an index of normal fetal thyroid development in mothers with hyperthyroidism treated with necessary antithyroid medication.

Autoimmune Thyroid Disease and Pregnancy: Relevance for the Child

As a group, the autoimmune thyroid diseases, including Graves' disease, Hashimoto's thyroiditis, and primary myxedema, are among the most common endocrine disorders encountered during pregnancy. Therefore, a substantial number of offspring will grow and develop in utero under conditions of maternal autoimmune thyroid disease and may be exposed to abnormal maternal thyroid function, maternal thyroid antibodies, and/or numerous therapeutic agents used to manage maternal thyroid dysfunction. This article reviews the effects that these various aspects of maternal autoimmune thyroid disorders can have on pregnancy outcome, as well as on the physical growth, neuropsychological development, and thyroid status of the developing fetus and neonate.

Mode of Action: Developmental Thyroid Hormone Insufficiency—Neurological Abnormalities Resulting From Exposure to Propylthiouracil

Because thyroid hormone is essential for normal brain development before and after birth, environmental chemicals that interfere with thyroid hormone signaling can adversely affect brain development. Adverse consequences of thyroid hormone insufficiency depend both on severity and developmental timing, indicating that environmental antithyroid factors may produce different effects at different developmental windows of exposure. Mechanistic studies can provide important insight into the potential impact of chemicals on human thyroid function, but relevance to humans must be systematically evaluated. This kind of analysis depends on data sets that include information about animals and humans. The drug 6-n-propyl-2-thiouracil (PTU) is used in animals to experimentally manipulate serum thyroid hormone levels, and in humans to treat patients, including pregnant women, with Graves' disease. A systematic analysis of the mode of action (MOA) of PTU in rats and in humans discloses similar modes of action. While the analysis predicts that PTU doses that produce thyroid hormone insufficiency in humans would adversely affect the developing brain, careful monitoring of PTU administration in pregnant and lactating humans keeps infant serum thyroid hormone levels within the normal range.

Nomograms of fetal thyroid measurements estimated by 2-dimensional sonography

PURPOSE

To build nomograms of fetal thyroid circumference (FTC), fetal thyroid area (FTA), and fetal thyroid transverse diameter (FTTD) throughout gestational age (GA).

METHOD

Between January 2006 and July 2006, FTC, FTA, and FTTD were measured once in 196 normal fetuses examined at a GA of 22-35 weeks. Inclusion criteria were a healthy mother with normal maternal thyrotropin level during pregnancy, a singleton pregnancy with normal fetal morphology on sonography, and GA confirmed via first-trimester sonographic examination.

RESULTS

Mean FTC, FTA, and FTTD ranged from 3.21 cm, 0.58 cm(2), and 1.19 cm at 22 weeks to 5.11 cm, 1.69 cm(2), and 1.89 cm at 35 weeks, respectively. Linear regression analysis yielded the following formulas for FTC, FTA, and FTTD according to GA: FTC (cm) = 0.146 x GA (weeks); FTA (cm(2)) = -1.289 + 0.085 x GA (weeks); FTTD (cm) = 0.054 x GA (weeks). The following logarithmic formulas were obtained for the expected fetal thyroid measurements according to estimated fetal weight (FW): FTC (cm) = -4.791 + 1.265 x logN FW; FTA (cm(2)) = -1.676 + 0.455 x logN FW; and FTTD (cm) = 0.399 + 0.001 x logN FW.

CONCLUSION

We describe new nomograms of fetal thyroid measurements throughout gestation that may be useful in case of thyroid dysfunction.

Twin pregnancy with a coexisting hydatiform mole and liveborn infant: complicated by maternal hyperthyroidism and neonatal hypothyroidism

A twin pregnancy with a coexisting complete hydatiform mole and a healthy fetus is rare. Associated with this condition are potentially serious maternal and fetal complications. We describe a case of a woman, 23/40 pregnant, who was diagnosed with a twin pregnancy complicated by a hydatiform mole, vaginal bleeding, hyperthyroidism and preterm labour at 26/40. Her hyperthyroidism was successfully treated with propylthiouracil. The preterm labour resulted in the livebirth of a healthy male infant. The baby developed biochemical hypothyroidism post-natally. The baby's thyroid function tests were unexpected, revealing a low T4 and a low-normal thyroid stimulating hormone. This is the first case reported in the literature to describe an infant's clinical and biochemical thyroid status after gestational trophoblastic disease complicated by hyperthyroidism.

Propylthiouracil Versus Methimazole in Treatment of Graves' Disease During Pregnancy

OBJECTIVE:

To evaluate the evidence supporting the use of propylthiouracil (PTU) versus methimazole for the treatment of Graves' disease during pregnancy.

DATA SOURCES:

An English-language literature search was conducted using MEDLINE (1966–March 2007). Identified articles were then reviewed for additional sources. Search terms included hyperthyroidism, Graves' disease, pregnancy, propylthiouracil, and methimazole.

STUDY SELECTION AND DATA EXTRACTION:

All clinical trials and case reports that were published in English and reported either subjective or objective outcomes were reviewed.

DATA SYNTHESIS:

Rationale supporting the use of PTU over methimazole in treatment of Graves' disease during pregnancy is limited. Theories suggesting that PTU has less placental transfer to the fetus than methimazole are not supported by current literature. Studies demonstrating a causal relationship between methimazole use during pregnancy and congenital anomalies and/or fetal hypothyroidism do not exist.

CONCLUSIONS:

The selection of PTU versus methimazole for the treatment of Graves' disease during pregnancy should not be based solely on the following assumptions: that PTU crosses the placenta less than methimazole, that PTU leads to less fetal hypothyroidism, or that exposure to methimazole during pregnancy leads to decreased intellectual function in children. However, due to a possible association between the use of methimazole during pregnancy and fetal anomalies such as aplasia cutis, esophageal atresia, and choanal atresia, methimazole may be a less desirable first-line treatment for Graves' disease in pregnancy than PTU. Therefore, in the absence of a compelling indication for the use of methimazole, PTU should still be considered as the first-line agent in the treatment of Graves' disease during pregnancy. Methimazole should be considered a viable second choice if the patient is intolerant to PTU, has an allergic reaction to PTU, or fails to become euthyroid while receiving PTU.

CONCLUSIONES:

La selección de PTU versus metimazole en el tratamiento de enfermedad de Graves durante el embarazo no debe ser basada en la siguiente información: 1que PTU cruza la placenta a un menor grado que metimazole, que PTU se asocia con menos hipotiroidismo fetal, ó que la exposición a metimazole durante el embarazo lleva a una disminución en la función intelectual en niños. Sin embargo, debido a una posible asociación entre el uso de metimazole durante el embarazo y anormalidades fetales tales como aplasia cutis, atresia esofageal y atresia choanal, metimazole podría ser una alternativa de primera línea menos deseable para el tratamiento de enfermedad de Graves durante el embarazo que PTU. Por lo tanto, en la ausencia de indicación contundente para el uso de metimazole, PTU debe considerarse el agente de primera línea en el tratamiento de enfermedad de Graves durante el embarazo. Sin embargo, metimazole puede considerarse un agente alterno si el paciente no tolera el PTU, tiene reacción alérgica a PTU o falla en convertir a eutirodeo con PTU. RÉSUMÉ: Il existe peu de justification à l'utilisation du PTU plutôt que du methimazole. Certaines théories suggérant que le PTU traverse moins la barrière placentaire ne sont pas, à l'heure actuelle, supportées par des évidences. Les études démontrant une relation de cause à effet entre le methimazole et des anomalies congénitales et/ou de l'hypothyroïdisme chez le fétus n'existent pas.

Thyroid medications during pregnancy

Euthyroid women experience dramatic changes in their thyroid physiology in order to accommodate the presence of placental and fetal tissues. These adaptations to the pregnant state make it crucial to develop reliable trimester-specific intervals for thyroid parameters. Use of non-pregnant reference intervals could lead to erroneous assessment of thyroid status in this rapidly changing hormonal environment. Only with a full appreciation of physiologic changes in thyroid parameters during a euthyroid pregnancy, can thyroid dysfunction be appropriately diagnosed and managed. Iodine sufficiency during pregnancy can be achieved with supplementation using a multivitamin. Both hypothyroidism and hyperthyroidism should be diagnosed using the appropriate reference intervals for pregnancy. Hypothyroid women are best treated with a specific brand of levothyroxine. Hypothyroidism should ideally be treated prior to conception. If newly recognized during pregnancy, it should be fully treated as early as possible. Frequent monitoring of thyroid status is essential as many women demonstrate an increased requirement for thyroid hormone during the first trimester. Although mild hyperthyroidism may be well tolerated during pregnancy, overt hyperthyroidism requires treatment. Thionamides are the mainstay of therapy. Following their initiation, close monitoring is required to avoid maternal and fetal hypothyroidism. There are occasional circumstances when other medical therapy or surgical therapy may be employed for hyperthyroidism. Thyroidectomy is generally safe in the second trimester in an appropriately prepared woman. There is limited data about the role and safety of oral contrast agents, iodine, amiodarone, and perchlorate. Radioiodine therapy is contradicted during pregnancy.

Pregnancy complicated with pulmonary edema due to hyperthyroidism

Hyperthyroidism is one of the most common causes of cardiac failure. Blood volume expands greatly during pregnancy, especially after the last part of the second trimester. Such expansion exacerbates the symptoms of heart failure and accelerates the development of pulmonary edema when abnormal thyroid function is not well controlled. Two cases of pregnancy complicated with congestive heart failure and pulmonary edema due to hyperthyroidism are reported here. Both patients did not receive treatment for hyperthyroidism during pregnancy, and both sought clinical help during the third trimester. The clinical problems were resolved by medical management before delivery.

Graves disease in childhood: a review of the options for diagnosis and treatment

While diagnosing Graves disease in childhood and adolescence does not usually present specific problems, the treatment of hyperthyroidism is still controversial. In particular, with regard to the use of radioiodine therapy, strategies vary between many European and North American pediatric endocrinology centers. After the diagnosis is made, antithyroid drug treatment with methimazole (thiamazole), carbimazole, or propylthiouracil should be performed with caution, in particular, because of severe adverse effects, such as agranulocytosis or hepatitis, that are found in up to 1% of patients. Antithyroid drug treatment should not be continued long-term, particularly since definitive remission cannot be expected in more than 30-40% of patients. In contrast, the risk of severe adverse effects is still present, and the risk of thyroid carcinoma increases with time and appears to be considerably higher than after radioiodine treatment. To a great extent, the success of surgery depends on the skills of a trained surgeon. The question of whether to perform total or subtotal thyroidectomy is yet to be resolved. Surgery should be considered in patients with a large thyroid gland (>80g), severe ophthalmopathy, and a lack of remission on antithyroid drug treatment. Success rates have increased to up to 97%, while severe adverse effects (laryngeal nerve palsy, hypoparathyroidism) occur in approximately 4% of patients. Mortality is below 0.1%. Radioiodine treatment in children >5 years of age does not appear to be associated with an increased risk of thyroid carcinoma; however, long-term data are lacking. Compared with the surgical approach, success rates are lower, particularly if low doses of radioiodine are used. In general, adverse effects are less prevalent than in patients who have undergone surgery.