Pregnancy outcome in women treated with methimazole or propylthiouracil during pregnancy

Autoimmune Thyroid Diseases

Autoimmune thyroid diseases (AITDs) include a wide spectrum of thyroid diseases affecting more commonly women than men. The most frequent forms are Graves' Disease (GD) and Hashimoto's thyroiditis / Autoimmune Thyroiditis (AIT), but there are also other immunogenic destructive forms of thyroiditis, that is, silent and postpartum thyroiditis. In the last decade, AITDs and other inflammatory thyroid diseases related to anti-tumor molecular drugs are more frequently seen due to the widespread use of tyrosine kinase inhibitors (TKIs) and immune checkpoint inhibitors (ICPIs). Autoimmune thyroiditis related to SARS-CoV-2 infection has been a novel entity in recent years. Graves' Disease and AIT may shift from hyperthyroidism to hypothyroidism, which may complicate the differential diagnosis and further treatment strategy. Moreover, all AITDs may manifest with thyrotoxicosis (a clinical condition marked with high serum levels of thyroid hormones) which has to be distinguished from hyperthyroidism (increased thyroid hormone production and secretion as a result of hyperfunctioning thyroid gland) due to different therapeutic approaches. Nuclear medicine techniques, such as radioiodine uptake (RAIU) and thyroid scintigraphy, using 99mTc- pertechnetate (Na[99mTc]TcO4) or 123-Iodine (Na[123I]I), have a crucial role in the differential diagnosis. Measurement of thyroid antibodies, e.g. thyroid peroxidase antibodies (TPO) and thyrotropin receptor antibodies (TRAb), as well as thyroid ultrasound, are complementary methods in the evaluation of thyroid disorders.

Effects of Methimazole vs Propylthiouracil in Newborns: A Comparative Review

Hyperthyroidism is more common in women and the sensitivity of thyroid function changes during pregnancy. Excess levels of thyroid hormones and thioamides have a major impact on maternal and fetal outcomes. Our aim was to perform an extensive literature review and provide relevant details concerning the analytical and clinical aspects of the potential effects of the two main drugs used (methimazole and propylthiouracil) in newborns. A thorough literature review was conducted using PubMed and Google Scholar databases. In total, 10 relevant studies were identified and data from these studies were extracted and then extrapolated into results after analysis. Three out of four studies that used methimazole and carbimazole, one and two, respectively, showed adverse fetal outcomes requiring surgical management for congenital anomalies like aplasia cutis, patent vitellointestinal duct, and gastroschisis. Out of the three studies that used propylthiouracil, one baby underwent surgery for bilateral pyelectasis, vesicovaginal fistula, anal stenosis, and polydactyly. The findings of the aforementioned studies provide enough evidence to imply that the use of methimazole and carbimazole to treat antenatal hyperthyroidism has worse fetal outcomes than the use of propylthiouracil. Also, given the paucity of data in the existing literature regarding propylthiouracil's effects on newborns, further studies in this demographic are needed.

Propylthiouracil-Induced Neonatal Goiter: An Avoidable Problem

We present a case of neonatal goiter caused by exposure to propylthiouracil (PTU) during pregnancy in this case report. The mother was treated with PTU while pregnant and had a history of Graves' illness. The baby had a neck tumor and was having breathing problems when they were first seen. A big thyroid gland was detected by a neck CT scan. This instance serves as a reminder of the significance of managing maternal thyroid problems appropriately during pregnancy as well as the requirement for careful thyroid function monitoring in newborns exposed to PTU. Given the possible hazards to the growing baby, it also calls into question whether PTU is an effective first-line treatment for maternal Graves' illness during pregnancy. This case report highlights the importance of shared decision-making with patients (by discussing different treatment options and their side effects).

Application of oral inorganic iodine in the treatment of Graves' disease

Iodine is a crucial trace element for the human body and the basic raw material for the synthesis of thyroid hormones. Oral inorganic iodine includes dietary iodine and therapeutic iodine, both of which are closely associated with thyroid immunity and metabolism. Graves' disease (GD), also known as diffuse toxic goiter, is characterized by hyperthyroidism and high iodine metabolism. Clinically, patients diagnosed with GD are often asked to limit iodine intake or even avoid iodine in their diet. The latest research has demonstrated that the interference of dietary iodine with antithyroid drugs (ATDs) treatment may be overestimated. In addition, as a medication for GD treatment, the administration of inorganic iodine has shown positive results in patients with mild hyperthyroidism, a low thyroid autoantibody concentration, a small thyroid volume, a high iodine diet and so on. Inorganic iodine may also be used as an alternative when patients experience side effects with traditional ATDs and for those who still prefer conservative treatment. Due to its low teratogenicity, blood toxicity and bone marrow toxicity, inorganic iodine plays a unique role in special populations, such as pregnant or lactating patients and patients receiving tumor radiotherapy or chemotherapy. In this review, the research progress, biological function, doses and effects, applicable populations and specific applications of dietary iodine and therapeutic iodine are summarized to provide references for the diagnosis and treatment of GD, thus improving the quality of life of GD patients.

Comparison of the safety between propylthiouracil and methimazole with hyperthyroidism in pregnancy: A systematic review and meta-analysis

OBJECTIVE

The purpose of this meta-analysis was to assess the safety of the anti-thyroid drugs (ATDs) propylthiouracil (PTU) and methimazole (MMI) in the treatment of hyperthyroidism during pregnancy.

METHOD

From inception until June 2, 2022, all available studies were searched in PubMed, Web of Science, Cochrane, EBSCO, Embase, Scopus, and CNKI.

RESULT

Thirteen articles satisfying the inclusion criteria were examined. Our meta-analysis indicated that pregnant women treated with MMI had a higher risk of congenital anomalies than those treated with PTU (OR 0.80, 95%CI 0.69-0.92, P = 0.002, I2 = 41.9%). Shifting between MMI and PTU during pregnancy did not reduce the risk of birth defects compared to PTU alone (OR 1.18, CI 1.00 to 1.40, P = 0.061, I2 = 0.0%). There were no statistically significant differences in hepatotoxicity (OR 1.54, 95%CI 0.77-3.09, P = 0.221, I2 = 0.0%) or miscarriage (OR 0.89, 95%CI 0.72-1.11, P = 0.310, I2 = 0.0%) between PTU and MMI exposure.

CONCLUSION

The study confirmed propylthiouracil is a safer alternative to methimazole for treating hyperthyroidism in pregnant women, and it is appropriate to treat maternal thyroid disease with PTU during the first trimester of pregnancy. However, it is not clear whether switching between propylthiouracil and methimazole is a better option than treating PTU alone during pregnancy. Further studies on this matter may be needed to develop new evidence-based guidelines for the treatment of pregnant women with hyperthyroidism.

Efficacy of propylthiouracil in the treatment of pregnancy with hyperthyroidism and its effect on pregnancy outcomes: A meta-analysis

Background

Hyperthyroidism affects about 0.2%-2.7% of all pregnancies, and is generally treated with propylthiouracil (PTU). However, previous studies about the effects of propylthiouracil on maternal or foetal are contentious.

Objective

This meta-analysis was carried out to investigate the safety and efficacy of propylthiouracil during pregnancy.

Materials and methods

PubMed, EBSCO, Embase, Scopus, Web of Science, Cochrane, CNKI, Wanfang and VIP database were searched from inception until August 31, 2021 for all available randomized controlled trials (RCTs) or cohort studies that evaluated the efficacy of propylthiouracil and its effects on pregnancy outcomes. Odds ratio (OR) and 95% confidence interval (CI) were used for binary variables, weighted mean difference (WMD) and 95% confidence interval (CI) were used for continuous variables. RevMan5.4 and Stata 16.0 were used for performing the meta-analysis.

Results

The researchers examined data from 13 randomized controlled trials and cohort studies involving 18948 infants. Congenital anomalies were not significantly associated with PTU in the pooled results (OR = 1.03, 95%CI: 0.84–1.25, P = 0.80, I² = 40.3%). There were no statistically significant differences in neonatal hypothyroidism (OR = 0.55, 95%CI: 0.06–4.92, P = 0.593, I² = 57.0%) or hepatotoxicity (OR = 0.34, 95%CI: 0.08–1.48, P = 0.151, I² = 0.0%) exposed to PTU compared to the control group. The serum levels of FT3, FT4, TT3, and TT4 were significantly lower in the propylthiouracil group compared to the control group.

Conclusion

This meta-analysis confirmed the beneficial effects of propylthiouracil treatment, namely the risks of adverse pregnancy outcomes were not increased, and it also proved PTU’s efficacy in the treatment of pregnant women with hyperthyroidism. The findings supported the use of propylthiouracil during pregnancy with hyperthyroidism in order to improve clinical pregnancy outcomes in patients with thyroid dysfunction.

MANAGEMENT OF THYROTOXICOSIS AND PREGNANCY: Review of the current literature and an update of the care pathway

Pregnancy can be complicated by hyperthyroidism or thyrotoxicosis. Diagnosis is founded on an increase in free thyroid hormones and low TSH. The most frequent etiologies are Graves' disease, an autoimmune disease linked to stimulatory anti-TSH receptor antibodies, and non-autoimmune gestational hyperthyroidism linked to the TSH-like activity of the chorionic growth hormone (hCG). During pregnancy, thyrotoxicosis can entail maternal, obstetrical and fetal or neonatal complications. Graves' hyperthyroidism may be responsible for fetal and neonatal hyperthyroidism due to placental transfer of stimulatory anti-TSH receptor antibodies. During pregnancy, treatment of thyrotoxicosis must restore normal thyroid function in the mother without affecting fetal thyroid function. The recent reassessment of the prevalence of teratogenic effects in children of women treated with antithyroid drugs in the first weeks of gestation should orient the care pathway before and during pregnancy for women of child-bearing age with hyperthyroidism linked to Graves' disease.

Pregnancy Outcomes among Women with Graves' Hyperthyroidism: A Retrospective Cohort Study

OBJECTIVE

The primary objectives of this study are to compare the rates of preterm birth; fetal growth restriction and low birth weight between the following groups: (1) pregnant women treated for thyrotoxicosis and low-risk pregnancies; (2) between pregnant women with thyrotoxicosis with no need of medication and low-risk pregnancies; and (3) between those treated with MMI and PTU.

METHODS

The medical records of singleton pregnancies with thyrotoxicosis were comprehensively reviewed. Low-risk pregnancies matched for age and parity were randomly recruited as controls. The obstetric outcomes were compared between both groups; the outcomes of various subgroups of the thyrotoxicosis group were also compared.

RESULTS

A total of 408 pregnant women with thyrotoxicosis were recruited. Compared with the controls; the women of the thyrotoxicosis group had significantly higher rates of low birth weight (LBW) (23.7% vs. 17.7%; p: 0.036), preterm birth (19.3% vs. 12.3%; p: 0.007), preeclampsia (8.5% vs. 4.4%; p: 0.019) and cesarean section (21.5% vs. 16.0%; p: 0.046). In the thyrotoxicosis group; 67; 127; and 158 patients were treated with MMI; PTU and no anti-thyroid drug (ATD), respectively. All obstetric outcomes were comparable between the women treated with PTU and those with MMI; and between the controlled and uncontrolled groups. However, women who needed ATD had significantly higher rates of LBW and preterm birth than those without medications.

CONCLUSIONS

Thyrotoxicosis, whether treated or not needing ATDs, was significantly associated with an increased risk of adverse pregnancy outcomes. Also, active disease, indicated by the need for ATD significantly increased the risk of such adverse outcomes; whereas the patients treated with MMI or PTU had comparable adverse outcomes.

Exposure to Propylthiouracil in the First Trimester of Pregnancy and Birth Defects: A Study at a Single Institution

Context

Medical treatment of Graves disease during the first trimester has been the subject of controversy ever since treatment with an antithyroid drug during the first trimester was reported to possibly be associated with an increased risk of birth defects in newborns.

Objective

We investigated whether the incidence of birth defects among newborns born to mothers with Graves disease (GD) treated with propylthiouracil (PTU) during the first trimester of pregnancy was higher than in a control group that was not exposed to any medication.

Methods

We reviewed the cases of 1913 women with GD who gave birth between January 1, 2015, and May 31, 2019. Detailed information concerning the outcome of pregnancy and the presence of birth defects was collected at the first visit after the delivery and again 1 year after delivery. We classified the mothers and infants into 3 groups according to the treatment the mother had received for GD in the first trimester of pregnancy: a group in which the mothers had been treated with PTU alone (PTU group), a group in which the mothers had not been treated with any medication (control group), and a group in which the mothers had received some other medical treatment, such as thiamazole, potassium iodide, or 2 or more drugs (other treatment group).

Results

The incidence of malformed infant births was 5.5% (30/541 infants) in the PTU group and 5.7% (27/ 475 infants) in the control group. There were no specific birth defects in the PTU group, and there were no significant differences between PTU dosages or maternal thyroid function according to whether mothers had delivered a child with a birth defect.

Conclusion

The results of our retrospective study showed that treatment with PTU during the first trimester of pregnancy did not increase the incidence of birth defects among newborns.

Maternal hyperthyroidism and pregnancy outcomes: A population-based cohort study

OBJECTIVE

Maternal hyperthyroidism and antithyroid medications have been associated with adverse pregnancy and perinatal outcomes. This nationwide register-based study investigated the association of maternal hyperthyroidism and antithyroid drug (ATD) use with pregnancy outcomes and included all singleton births in Finland between 2004 and 2013 (N = 571 785).

DESIGN, PATIENTS AND MEASUREMENTS

Hyperthyroid mothers were identified in the Medical Birth Register, and data on ATD use before and/or during pregnancy were collected from the Prescription Register. The odds ratios, with 95% confidence intervals, for adverse outcomes among hyperthyroid mothers and mothers without thyroid disease were compared using logistic regression.

RESULTS

In total, 2144 (0.37%) of all the women had diagnoses of hyperthyroidism, and 580 (27%) of these women had used ATDs before and/or during pregnancy. Compared to the mothers without thyroid disease, maternal hyperthyroidism was associated with older age, multiparity, smoking, previous miscarriages, and overweight or obesity. The mothers diagnosed with hyperthyroidism also had increased odds of gestational hypertensive disorders, caesarean sections, placental abruptions, preterm births, small-for-gestational-age newborns and neonatal intensive care unit treatment. The odds of pregnancy and/or perinatal complications were higher among those who had used ATDs (indicative of active disease), but those who had not received ATD treatment also had increased odds of such complications compared to the mothers without thyroid disease.

CONCLUSIONS

Women with active hyperthyroidism and those with histories of hyperthyroidism should be considered at risk of developing pregnancy and perinatal complications and should therefore be monitored during pregnancy.

Teratogen update: Antithyroid medications

OBJECTIVE

Thyroid disorders including hyperthyroidism are common during pregnancy. Untreated hyperthyroidism can result in adverse outcomes for pregnancy.

METHODS

Iodine, propylthiouracil (PTU), carbimazole (CMZ), and methimazole (MMI) are common medications for hyperthyroidism treatment. The literature regarding antithyroid medication use in pregnancy and breastfeeding is reviewed.

RESULTS

Animal studies for PTU have suggested congenital anomalies while animal studies for MMI have only indicated adverse outcomes at higher doses than used in humans. Epidemiological studies have noted an increased risk of congenital anomalies for PTU less often than CMZ or MMI but the epidemiological evidence remains mixed. A pattern of anomalies has been described for CMZ and MMI, from both case and epidemiological studies, including choanal atresia, aplasia cutis congenita, and other facial, heart, gastrointestinal, and skin anomalies. Closer examination of cases indicates that a few cases of the anomalies have occurred without exposure to CMZ or MMI and outside of the proposed critical period. PTU has a small risk of hepatotoxicity which rarely results in liver transplantation and death. Some authors have suggested that PTU be prescribed in early pregnancy and switched to MMI in late pregnancy. Untreated hyperthyroidism, from either a lack of medications or switching medications during the first trimester, may also increase the chance of congenital anomalies. Multiple case studies and larger epidemiological studies have failed to provide clear, consistent outcomes for the use of PTU, CMZ, and MMI in pregnancy. MMI and PTU both enter the breastmilk in small amounts.

CONCLUSION

Additional research is needed to assist in the medical management and exposure counseling of pregnant and breastfeeding women with hyperthyroidism.

Management of thyrotoxicosis during pregnancy

Thyrotoxicosis during pregnancy should be adequately managed and controlled to prevent maternal and fetal complications. The evaluation of thyroid function in pregnant women is challenged by the physiological adaptations associated with pregnancy, and the treatment with antithyroid drugs (ATD) raises concerns for the pregnant woman and the fetus. Thyrotoxicosis in pregnant women is mainly of autoimmune origin, and the measurement of thyroid stimulating hormone-receptor antibodies (TRAb) plays a key role. TRAb helps to distinguish the hyperthyroidism of Graves' disease from gestational hyperthyroidism in early pregnancy, and to evaluate the risk of fetal and neonatal hyperthyroidism in late pregnancy. Furthermore, the measurement of TRAb in early pregnancy is recommended to evaluate the need for ATD during the teratogenic period of pregnancy. Observational studies have raised concern about the risk of birth defects associated with the use of ATD in early pregnancy and challenged the clinical management and choice of treatment.

Antithyroid drugs and birth defects

Antithyroid drugs (ATDs) are preferred for the treatment of hyperthyroidism caused by Graves’ disease in pregnant women. The drugs have been a recognized treatment for decades, and a general risk of side effects is known. For the use of ATDs in pregnancy, a concern about teratogenic side effects has been brought forward since the 1970s. In more recent years, a number of large observational studies have added new evidence and quantified the risk of birth defects associated with different types of ATDs. The findings that both Methimazole (MMI) and Propylthiouracil (PTU) are associated with birth defects have challenged the clinical recommendations on the treatment of hyperthyroidism in pregnancy, and certain aspects remain unclarified. In this review, the current evidence on the risk of birth defects associated with the use of ATDs in early pregnancy is described, and determinants of causality are discussed. This includes the current evidence of a biological gradient and the role of maternal thyroid function per se. Finally, clinical aspects of the timing and type of treatment is discussed, and future perspectives are addressed. Current evidence corroborates a risk of birth defects associated with MMI while more evidence is needed to determine the teratogenic potential of PTU. Detailed assessment of type and timing of exposure in large cohorts are needed. Moreover, studies investigating alternative or new treatments are warranted.

Safety of antithyroid drugs in pregnancy: update and therapy implications

Introduction: The thionamide antithyroid drugs, methimazole (MMI), its pro-drug derivative carbimazole (CMZ), and propylthiouracil (PTU) are the mainstay of treatment for hyperthyroidism in pregnancy. However, antithyroid drugs carry risks of adverse effects that can affect fetal and maternal well-being.Areas covered: This review provides an update on the safety of antithyroid drugs in pregnancy, focusing on the most serious concerns of severe liver disease and congenital anomalies.Expert opinion: PTU-induced liver disease is uncommon but can run a catastrophic course in pregnancy with a risk of liver failure and threats to maternal or fetal survival. Acute pancreatitis is a relatively rare occurrence that has been linked to thionamide use in a handful of reports in non-pregnant individuals. Observational studies on the risk of birth defects with antithyroid drug exposure in pregnancy overall show an increase in birth defect risk with exposure to CMZ/MMI, and to a lesser extent, PTU. Further studies are required to determine whether the currently recommended approach of switching between thionamide drugs in pregnancy improves outcomes. Ultimately, a preventative strategy of offering definitive therapy to hyperthyroid women of childbearing potential offers the best approach to truly reduce the risks of antithyroid drug adverse effects in pregnancy.

Treatment of Graves' hyperthyroidism with thionamides: a position paper on indications and safety in pregnancy

CONTEXT

Graves' disease affects 3% of women and 0.5% of men in the general population. The first line treatment of Graves' hyperthyroidism is based on the administration of antithyroid drugs (ATD), propylthiouracil (PTU), methimazole (MMI) and carbimazole. A recent warning from the Italian Drug Agency (Agenzia Italiana del Farmaco AIFA) reported the risk of MMI-induced acute pancreatitis. In addition, AIFA highlighted the possible association of MMI treatment during the first trimester of pregnancy with congenital malformations, thus recommending the use of effective contraceptive methods in women of childbearing age treated with MMI.

METHODS AND RESULTS

Revision of literature reported less than ten cases of the alleged MMI pancreatitis, allowing the inclusion of MMI in class III drug regarding the relative risk for drug-induced pancreatitis. Data available on the effect of hyperthyroidism per se on the risk of fetal malformations, although scanty, are sufficient to recommend treatment with ATD of the hyperthyroid pregnant woman. Case reports and population studies either suggesting or not suggesting MMI-induced fetal malformations do not allow unquestionable conclusions on this matter.

CONCLUSIONS

This consensus by experts from Italian Endocrine and Gynecologic Scientific Societies has edited recommendations derived form the available data and published guidelines of International Scientific Societies.

Maternal Thyroid Function, Use of Antithyroid Drugs in Early Pregnancy, and Birth Defects

CONTEXT

Antithyroid drug (ATD) therapy in early pregnancy is associated with birth defects, but more data are needed to substantiate the risk associated with different types of ATD. Furthermore, the role of abnormal maternal thyroid function per se remains unclarified.

OBJECTIVE

To evaluate the risk of birth defects associated with the use of ATD in an extended nationwide cohort and the role of abnormal maternal thyroid function in birth cohorts including stored maternal blood samples from early pregnancy.

PARTICIPANTS

Danish pregnant women and their live-born children, including 1,243,353 children from a Nationwide Register-Based Cohort (NRBC), 1997 to 2016; 8830 children from the Danish National Birth Cohort (DNBC), 1997 to 2003; and 14,483 children from the North Denmark Region Pregnancy Cohort (NDRPC), 2011 to 2015.

MAIN OUTCOME MEASURES

Birth defects diagnosed before 2 years of age.

RESULTS

In the NRBC, altogether 2718 (0.2%) children had been exposed to ATD in early pregnancy. The overall frequency of birth defects was 6.7% (95% CI, 6.7% to 6.8%) in nonexposed children and higher after exposure to methimazole/carbimazole (9.6%; 95% CI, 8.2% to 11.2%) and propylthiouracil (8.3%; 95% CI, 6.7% to 10.3%). On the other hand, the frequency of maternal thyroid dysfunction in early pregnancy was similar in the random cohort and in cases of birth defect in the DNBC (12.4 vs 12.6%, P = 0.8) and the NDRPC (15.1 vs 15.4%, P = 0.8).

CONCLUSIONS

Results corroborate an increased risk of birth defects associated with the use of ATD in early pregnancy and suggest that abnormal maternal thyroid function is not a major risk factor for birth defects.

Hyperthyroid heart disease in pregnancy: Retrospective analysis of a case series and review of the literature

BACKGROUND

Hyperthyroidism in pregnancy may pose a great threat to maternal and fetal health. The risk of hyperthyroid heart disease (HHD), even heart failure, is significantly elevated in pregnant women.

AIM

To investigate the clinical characteristics, prognosis, and therapy of HHD in pregnant women.

METHODS

We searched the patient registry data at West China Second University Hospital of Sichuan University in Chengdu, China, following the approval by the Ethics Committee. We retrospectively analyzed the clinical characteristics of pregnant women diagnosed with HHD. The medical records of women with HHD during pregnancy from January 2012 to December 2017 were obtained from the electronic medical records system. All the included patients were followed in outpatient clinics and by telephone interviews until October 2018.

RESULTS

A total of 155 patients were diagnosed with thyrotoxicosis, of whom six were diagnosed with HHD. Three of them had regular antenatal care. Two patients were complicated with acute heart failure attacks, and one of them had a stillbirth. Both of these patients had a long history of Graves’ disease with poor treatment compliance. Treatments of precipitating factors such as the control of infection could relieve the symptoms and prolong gestation for a better prognosis. Hyperthyroid heart failure could be controlled with aggressive diuretics and management of the coexisting complications. Intense monitoring and timely anti-heart failure treatment were crucial in patients with severe cardiac damage. Our findings indicated the importance of regular antenatal care and treatment adherence in patients with hyperthyroidism.

CONCLUSION

The timely and accurate diagnosis of HHD and the implementation of effective management are important for a better prognosis in pregnant women with HHD. Improvement in patients’ awareness of thyrotoxicosis is needed.

Graves' hyperthyroidism in pregnancy

PURPOSE OF REVIEW

Graves' hyperthyroidism is associated with significant obstetric, maternal, fetal, and neonatal complications. Early diagnosis and an understanding of the management of Graves' hyperthyroidism in pregnancy can help to prevent these complications. Antithyroid drugs (ATD) should be avoided in early pregnancy, given their association with congenital malformations.

RECENT FINDINGS

TSH-receptor antibodies (TRAb) are integral in the management of Graves' hyperthyroidism in pregnancy and in the preconception period. TRAb are indicative of the current activity of Graves' hyperthyroidism and the likelihood of relapse. Furthermore, TRAb predicts the risk of fetal and neonatal hyperthyroidism.The incidence of congenital malformations is roughly the same for propylthiouracil (PTU) and methimazole (MMZ). Exposure to both ATDs in early pregnancy has been associated with increased incidence of congenital malformations compared with exposure to either ATD alone.

SUMMARY

The goal of the physician is maintaining euthyroidism throughout pregnancy and delivery of a healthy, euthyroid baby. An understanding of the natural progression of Graves' hyperthyroidism in pregnancy and the proper utilization of TRAb enables the physician to minimize the risks associated with Graves' hyperthyroidism and side effects of ATDs unique to pregnancy. The physician should prioritize preconception counseling in women with Graves' hyperthyroidism in order to avoid hyperthyroidism and having to use ATDs in pregnancy.

Hyperthyroidism in the pregnant woman: Maternal and fetal aspects

Hyperthyroidism during pregnancy is uncommon. Nonetheless, prompt identification and adequate management of hyperthyroidism in a pregnant woman is essential, because uncontrolled thyrotoxicosis significantly increases the risk of maternal and fetal complications. Also, fetal prognosis may be affected by the transplacental passage of maternal thyroid stimulating antibodies or thyrostatic agents, both of which may disrupt fetal thyroid function. Birth defects have been reported in association with the use of antithyroid drugs during early pregnancy. Although rarely, offspring of mothers with Graves’ disease may develop fetal/neonatal hyperthyroidism, the management of which requires a close collaboration between endocrinologists, obstetricians, and neonatologists.

Because of the above considerations, the management of pregnant and lactating women with hyperthyroidism requires special care, bearing in mind that both maternal thyroid excess per se and related treatments may adversely affect the newborn’s health.

In this review we discuss the diagnosis and management of hyperthyroidism in pregnancy, along with the impact of thyrotoxicosis and medications on fetal outcome.

Graves' hyperthyroidism in pregnancy: a clinical review

Background

Graves’ hyperthyroidism affects 0.2% of pregnant women. Establishing the correct diagnosis and effectively managing Graves’ hyperthyroidism in pregnancy remains a challenge for physicians.

Main

The goal of this paper is to review the diagnosis and management of Graves’ hyperthyroidism in pregnancy. The paper will discuss preconception counseling, etiologies of hyperthyroidism, thyroid function testing, pregnancy-related complications, maternal management, including thyroid storm, anti-thyroid drugs and the complications for mother and fetus, fetal and neonatal thyroid function, neonatal management, and maternal post-partum management.

Conclusion

Establishing the diagnosis of Graves’ hyperthyroidism early, maintaining euthyroidism, and achieving a serum total T4 in the upper limit of normal throughout pregnancy is key to reducing the risk of maternal, fetal, and newborn complications. The key to a successful pregnancy begins with preconception counseling.

Risk of embryopathies with use of antithyroidal medications

PURPOSE OF REVIEW

Hyperthyroidism in pregnant women should be adequately treated to prevent maternal and fetal complications. The treatment of choice in pregnancy is antithyroidal medications (ATDs). The risk of embryopathies associated with the use of Methimazole (MMI) and Propylthiouracil (PTU) in early pregnancy is a matter of clinical attention and concern. This review describes current evidence and how scientific findings are reflected in current clinical guidelines.

RECENT FINDINGS

Embryopathies after the use of ATDs were previously mainly described in case reports and considered rare. Recent large observational studies, including nonexposed control groups, have quantified an increased risk of embryopathies associated with use of ATDs during pregnancy. Findings suggest a risk of embryopathies with the use of both MMI and PTU, but the pattern of embryopathies differs, and embryopathies with the use of PTU appear less severe.

SUMMARY

Current guidelines highlight the need for clinical attention on the use of ATDs in early pregnancy. Patients managed on ATDs for the treatment of hyperthyroidism should be counseled to report a pregnancy as early as possible. PTU is the recommended treatment in early pregnancy, but if the risk of relapse or worsening of hyperthyroidism is considered low, it is suggested that ATD treatment can be withdrawn followed by frequent monitoring of thyroid function.

Birth defects after use of antithyroid drugs in early pregnancy: a Swedish nationwide study

OBJECTIVE

Antithyroid drugs (ATDs) may have teratogenic effects, but more evidence is needed on the risk and types of birth defects after the use of methimazole (MMI) and propylthiouracil (PTU). This study aimed to evaluate the association between the use of ATDs in early pregnancy and birth defects.

DESIGN

Swedish nationwide register-based cohort study.

METHODS

The study included 684 340 children live-born in Sweden from 2006 to 2012. Exposure groups defined by maternal ATD use in early pregnancy were MMI (n = 162); PTU (n = 218); MMI and PTU (n = 66); ATD before or after, but not in pregnancy (n = 1551) and non-exposed (never ATD (n = 682 343)). Outcome was cumulative incidence of birth defects diagnosed before two years of age.

RESULTS

The cumulative incidence of birth defects was not significantly different in children exposed to MMI (6.8%, P = 0.6) or PTU (6.4%, P = 0.4) vs non-exposed (8.0%). For subtypes of birth defects, MMI was associated with an increased incidence of septal heart defects (P = 0.02). PTU was associated with ear (P = 0.005) and obstructive urinary system malformations (P = 0.006). A case of choanal atresia was observed after exposure to both MMI and PTU. The incidence of birth defects in children born to mothers who received ATD before or after, but not in pregnancy, was 8.8% and not significantly different from non-exposed (P = 0.3), MMI exposed (P = 0.4) or PTU exposed (P = 0.2).

CONCLUSIONS

MMI and PTU were associated with subtypes of birth defects previously reported, but the frequency of ATD exposure in early pregnancy was low and severe malformations described in the MMI embryopathy were rarely observed.

Effects of methimazole and propylthiouracil exposure during pregnancy on the risk of neonatal congenital malformations: A meta-analysis

Objective

The aim of this study was to determine the effect of exposure to different antithyroid drugs during pregnancy on the incidence of neonatal congenital malformations.

Methods

A meta-analysis was performed to compare the incidence of neonatal congenital malformations after exposure to different antithyroid drugs during pregnancy. Twelve studies that met the inclusion criteria were included in this meta-analysis. PubMed, Embase, and CENTRAL databases were searched from inception until January 2017. Study designs included case–control studies, prospective cohort studies, and retrospective cohort studies.

Results

Twelve studies involving 8028 participants with exposure to different antithyroid drugs during pregnancy were included in this study; however, only 10 studies involving 5059 participants involved exposure to different antithyroid drugs exactly during pregnancy. Our results indicated that exposure to methimazole (MMI)/carbimazole (CMZ) only during pregnancy significantly increased the risk of neonatal congenital malformations compared to no antithyroid drug exposure (OR 1.88; 95%CI 1.33 to 2.65; P = 0.0004). No differences were observed between propylthiouracil (PTU) exposure and no antithyroid drug exposure only during pregnancy (OR 0.81; 95%CI 0.58 to 1.15; P = 0.24). Exposure to MMI/CMZ only during pregnancy significantly increased the risk of neonatal congenital malformations compared to that associated with exposure to PTU (OR 1.90; 95%CI 1.30 to 2.78; P = 0.001).

Conclusion

For pregnant women with hyperthyroidism, exposure to MMI/CMZ significantly increased the incidence of neonatal congenital malformations compared to exposure to PTU and no antithyroid drug exposure; however, no differences were observed between PTU exposure and no antithyroid drug exposure.

Current challenges in the pharmacological management of thyroid dysfunction in pregnancy

INTRODUCTION

Thyroid dysfunction is common in pregnancy and has adverse fetal and maternal health consequences. A number of challenges in the management of gestational thyroid dysfunction remain unresolved including uncertainties in optimal thresholds for correction of hypothyroidism and strategies for pharmacological management of hyperthyroidism. Areas covered: We addressed key challenges and areas of uncertainty in the management of thyroid dysfunction in pregnancy. Expert commentary: Gestational thyroid hormone reference intervals vary according to population ethnicity, iodine nutrition, and assay method and each population should derive trimester specific reference intervals for use in pregnancy. Subclinical hypothyroidism and isolated hypothyroxinaemia are common in pregnancy but there is no consensus on the benefits of correcting these conditions. Although observational studies show potential benefits of levothyroxine on child neurocognitive function these benefits are have not been supported by two controlled trials. Carbimazole should be avoided in the first trimester of pregnancy due to risk of congenital anomalies but recent studies would suggest that this risk is present to a lesser magnitude with propylthiouracil. Current international guidelines recommend the use of propylthiouracil in the first trimester and switching to carbimazole for the remainder of pregnancy but the benefits and practicalities of this approach is unproven.

ENDOCRINOLOGY IN PREGNANCY: Pregnancy and the incidence, diagnosing and therapy of Graves' disease

Thyroid hormones are essential developmental factors, and Graves' disease (GD) may severely complicate a pregnancy. This review describes how pregnancy changes the risk of developing GD, how early pregnancy by several mechanisms leads to considerable changes in the results of the thyroid function tests used to diagnose hyperthyroidism, and how these changes may complicate the diagnosing of GD. Standard therapy of GD in pregnancy is anti-thyroid drugs. However, new studies have shown considerable risk of birth defects if these drugs are used in specific weeks of early pregnancy, and this should be taken into consideration when planning therapy and control of women who may in the future become pregnant. Early pregnancy is a period of major focus in GD, where pregnancy should be diagnosed as soon as possible, and where important and instant change in therapy may be warranted. Such change may be an immediate stop of anti-thyroid drug therapy in patients with a low risk of rapid relapse of hyperthyroidism, or it may be an immediate shift from methimazole/carbimazole (with risk of severe birth defects) to propylthiouracil (with less risk), or maybe to other types of therapy where no risk of birth defects have been observed. In the second half of pregnancy, an important concern is that not only the mother with GD but also her foetus should have normal thyroid function.

Management of hyperthyroidism due to Graves' disease: frequently asked questions and answers (if any)

Graves' disease is the most common cause of hyperthyroidism in iodine-replete areas. Although progress has been made in our understanding of the pathogenesis of the disease, no treatment targeting pathogenic mechanisms of the disease is presently available. Therapies for Graves' hyperthyroidism are largely imperfect because they are bound to either a high rate of relapsing hyperthyroidism (antithyroid drugs) or lifelong hypothyroidism (radioiodine treatment or thyroidectomy). Aim of the present article is to offer a practical guidance to the reader by providing evidence-based answers to frequently asked questions in clinical practice.

Hyperthyroidism

Hyperthyroidism is characterised by increased thyroid hormone synthesis and secretion from the thyroid gland, whereas thyrotoxicosis refers to the clinical syndrome of excess circulating thyroid hormones, irrespective of the source. The most common cause of hyperthyroidism is Graves' disease, followed by toxic nodular goitre. Other important causes of thyrotoxicosis include thyroiditis, iodine-induced and drug-induced thyroid dysfunction, and factitious ingestion of excess thyroid hormones. Treatment options for Graves' disease include antithyroid drugs, radioactive iodine therapy, and surgery, whereas antithyroid drugs are not generally used long term in toxic nodular goitre, because of the high relapse rate of thyrotoxicosis after discontinuation. β blockers are used in symptomatic thyrotoxicosis, and might be the only treatment needed for thyrotoxicosis not caused by excessive production and release of the thyroid hormones. Thyroid storm and hyperthyroidism in pregnancy and during the post-partum period are special circumstances that need careful assessment and treatment.

Congenital Bands with Intestinal Malrotation after Propylthiouracil Exposure in Early Pregnancy

Exposure to propylthiouracil in early pregnancy may be associated with an increased risk of birth defects. But the spectrum of associated congenital anomalies is not yet well defined. While preliminary reports suggest that most cases of propylthiouracil-associated birth defects are restricted to the preauricular and urinary systems, careful consideration should be given to other possible manifestations of teratogenicity. We propose that congenital bands may potentially represent a rare yet serious complication of propylthiouracil exposure in early pregnancy, possibly arising from an early mesenteric developmental anomaly. We report a case of a 17-day-old girl that presented with acute small bowel obstruction associated with intestinal malrotation arising from several anomalous congenital bands. Her mother was treated for Graves' disease during pregnancy with first trimester exposure to propylthiouracil but remained clinically and biochemically euthyroid at conception and throughout the duration of pregnancy. This case suggests that the use of propylthiouracil in early pregnancy may be associated with congenital bands and intestinal malrotation. More reports are needed to further support this association.

Antithyroid Drug Use in Pregnancy and Birth Defects: Why Some Studies Find Clear Associations, and Some Studies Report None

BACKGROUND

Rare cases of birth defects after the use of methimazole (MMI) or carbimazole to treat hyperthyroidism in early pregnancy have been reported since 1972, whereas propylthiouracil (PTU) has not been considered teratogenic. Recently, two studies reported birth defects after the use of MMI in early pregnancy to affect 2-4% of exposed children, and one study also found birth defects after the use of PTU. On the other hand, some published studies did not find associations between the use of thionamides and birth defects.

SUMMARY

The methods used in the two positive and the four negative reports are reviewed. The two positive studies included a sufficient number of children exposed to MMI (n = 1231 and 1097) to evaluate the studied outcomes, whereas the four negative studies included a much lower number of exposed children (n = 73, 108, 30, and 124). Considering PTU, the birth defects observed in one study were in general milder and tended to be diagnosed and registered only when they resulted in complications and led to surgery after one year of age. None of the negative studies has investigated outcomes after one year of age.

CONCLUSION

Studies finding no associations between early pregnancy exposure to antithyroid drugs and birth defects were either not sufficiently powered or did not study outcomes at optimal ages.