Putting propylthiouracil in perspective

Graves' disease in two pregnancies complicated by fetal goitrous hypothyroidism: successful in utero treatment with levothyroxine

BACKGROUND

Treatment of Graves' disease during pregnancy with antithyroid drugs (ATDs) poses a risk of inducing hypothyroidism and, thus, development of a goiter to the fetus.

PATIENT FINDINGS

We report two patients referred to our department after discovery of a fetal goiter by ultrasound examination in the second trimester of pregnancy. The women receiving 400 mg/day propylthiouracil and 10 mg/day thiamizole, respectively, had thyrotropin and total thyroxine values within the normal reference range but a lowered free thyroxine level. Fetal blood sampling by cordocentesis revealed severe fetal hypothyroidism as the cause of goiter development. Reduction of maternal ATD dose and injection of levothyroxine intra-amniotically quickly reduced the goiter size, and both babies were born euthyroid and without goiters.

SUMMARY

Two pregnant women with Graves' disease were overtreated with ATDs inducing iatrogenic goiter in the fetuses. Successful treatment with intra-amniotic levothyroxine injections rendered the babies euthyroid and nongoitrous at birth.

CONCLUSIONS

Correct interpretation of thyroid function tests during pregnancy in general--and during ATD therapy of Graves' disease in particular--is difficult. Awareness of pregnancy-related changes in maternal thyroid status, and a close teamwork among endocrinologists, obstetricians, and experts in fetal medicine, is pivotal in ensuring normal growth and development of the unborn child of these patients.

Comparison of methimazole and propylthiouracil in the management of children and adolescents with Graves' disease: efficacy and adverse reactions during initial treatment and long-term outcome

OBJECTIVE

The aim of this study was to compare the efficacy and adverse reactions during initial treatment and long-term outcome between children and adolescents with Graves' disease (GD) treated with propylthiouracil (PTU) and those treated with methimazole (MMI).

DESIGN, SETTING AND PARTICIPANTS

Retrospective and collaborative study. Children and adolescents with GD were divided into group M (MMI: n=64) and group P (PTU: n=69) and into four subgroups by initial dose: group M1 (<0.75 mg/kg of MMI, n=34), group M2 (> or = 0.75 mg/kg, n=30), group P1 (<7.5 mg/kg of PTU, n=24) and group P2 (> or = 7.5 mg/kg, n=45).

MAIN OUTCOME MEASURES

The duration for normalization of serum T4 on initial treatment, the incidence of adverse effects for one year and outcomes at 10 years after were compared.

RESULTS

Mean durations for normalization of T4 (+/- SD) were 1.7 +/- 1.0 months in group M and 2.3 +/- 2.4 in group P [not significant (NS)], while the mean duration in group P1 (3.1 +/- 3.3) was significantly longer than those in the other subgroups (M1: 1.9 +/- 1.2; M2: 1.4 +/- 0.7; P2; 1.7 +/- 1.3). No major adverse reaction was observed. Minor adverse effects occurred in 25.0% of cases in group M and 31.9% in group P (NS). The incidence in group P2 (44.4%) was significantly higher than those in group M1 (20.6%) and group P1 (8.3%). Remission rates did not differ between the MMI-treated group (35.0%, n=20) and PTU-treated group (50.0%, n=40).

CONCLUSIONS

PTU may not be suitable for initial use in children and adolescents with GD, even with the risk of major adverse reactions such as liver failure excluded.

Thyroid function in pregnancy

Advances in understanding the physiology of thyroid function in normal pregnancy have highlighted the importance of the consequences of abnormal function on obstetric outcome and foetal well-being. Pubmed search was done using the terms thyroid and pregnancy. Areas of agreement are the following: gestational normative reference ranges for thyroid function tests are required for proper interpretation of any abnormalities. Measurement of thyroid-stimulating antibodies and antithyroid peroxidase antibodies is useful for diagnosis of thyroid disease in pregnancy. Treatment of Graves' hyperthyroidism should be done with propylthiouracil for first trimester only, then carbimazole or methimazole. Patients on levothyroxine require an increase in dosage during gestation. Areas of controversy are the following: total thyroxine (TT4) versus Free T4 (FT4) assays in pregnancy. Screening for thyroid function in early gestation: should it be routinely performed on everyone? What tests are appropriate? Growing points are the following: physiology of thyroxine delivery to the foetus. Establishment of gestational thyroid hormone reference ranges. Evaluation of strategies to screen thyroid function in early pregnancy. Areas timely for developing research are the following: placental thyroid hormone physiology, thyroid hormone therapy and screening thyroid function.

Radioiodine treatment in pediatric Graves' disease and thyroid carcinoma

Graves' disease (GD) is the most common cause of hyperthyroidism in pediatric patients. Most pediatric thyroid cancer is differentiated thyroid cancer (DTC). The two diseases can be treated using different methods, such as antithyroid drug, radioactive iodine (RAI), and surgery for GD and surgery and RAI for DTC. RAI can be used to treat pediatric GD and DTC. In the article, we reviewed the RAI application in pediatric GD and DTC.

Hyperthyroidism and jaundice

Development of hyperbilirubinemia, concurrent or subsequent to hyperthyroidism, can be due to thyrotoxicosis per se, or due to drug treatment of hyperthyroidism. Other rare conditions: autoimmune thyroid disease, or causes unrelated to hyperthyroidism like viral hepatitis, alcohol abuse, sepsis, cholangitis, or as a side effect of certain medications. In this article, we review these causes of co-existent hyperthyroidism and jaundice. We also highlight the changes to be expected while interpreting thyroid function tests vis-a-vis liver function tests in this subgroup of patients.

Interventions for preventing and treating hyperthyroidism in pregnancy

BACKGROUND

Women with hyperthyroidism in pregnancy have increased risks of miscarriage, stillbirth, preterm birth, and intrauterine growth restriction; and they can develop severe pre-eclampsia or placental abruption.

OBJECTIVES

To assess the effects of interventions for preventing or treating hyperthyroidism in pregnant women.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (28 July 2010).

SELECTION CRITERIA

We intended to include randomised controlled trials comparing antithyroid treatments in pregnant women with hyperthyroidism.

DATA COLLECTION AND ANALYSIS

Two review authors would have assessed trial eligibility and risk of bias, and extracted data.

MAIN RESULTS

No trials were located.

AUTHORS' CONCLUSIONS

As we did not identify any eligible trials, we are unable to comment on implications for practice, although early identification of hyperthyroidism before pregnancy may allow a woman to choose radioactive iodine therapy or surgery before planning to have a child. Designing and conducting a trial of antithyroid drugs for pregnant women with hyperthyroidism presents formidable challenges. Not only is hyperthyroidism a relatively rare condition, both of the two main drugs used have potential for harm, one for the mother and the other for the child. More observational research is required about the potential harms of methimazole in early pregnancy and about the potential liver damage from propylthiouracil.

Liver failure due to antithyroid drugs: report of a case and literature review

Hyperthyroidism is a common endocrine disorder affecting 2% of females and 0.5% of males worldwide and antithyroid drugs constitute the first line of treatment in the majority of cases. These agents may cause severe adverse effects and among them liver failure, although rare, is a potential lethal one. This case illustrates the sudden and abrupt deterioration of hepatic function due to antithyroid drug administration. This case along with a concise literature review is presented aiming to increase the awareness of endocrinologists of possible fatal complications from the everyday use of common agents such as antithyroid drugs.

63 years and 715 days to the "boxed warning": unmasking of the propylthiouracil problem

715 days after potential problems related to PTU use in children were presented in a debate in front of the Lawson Wilkins Pediatric Endocrine Society (LWPES), the US Food and Drug Administration issued a “black-box” warning about the hepatotoxicity risk of the antithyroid drug propylthiouracil (PTU). This safety advisory followed the collective actions of academic societies, medical publishers, the National Institutes of Health, and the FDA. Considering that surgery and radioactive iodine are the legitimate treatment options for Grave Disease (GD), and are now the preferred alternative therapy in individuals who developed toxic reactions to MMI, the use of PTU should now be limited to exceptional circumstances and pregnancy. Long-term PTU therapy, especially in children, is not justifiable. The current advisory comes 63 years after the introduction of PTU for clinical use in 1947.

Thyroid dysfunction in pregnancy: optimizing fetal and maternal outcomes

Recent decades have seen a growing awareness of the threat posed by thyroid dysfunction in pregnancy on maternal, fetal and neonatal well-being. Uncontrolled hypothyroidism and hyperthyroidism are associated with adverse obstetrics and fetal outcomes and also affect neurointellectual development in the offspring. Excellent outcomes are, however, achievable with appropriate management. An understanding of the changes in thyroid hormone economy in pregnancy is crucial to the evaluation of thyroid status in pregnant patients with thyroid dysfunction. Furthermore, a balance must be maintained between the control of maternal disease and the requirements of the developing fetus. Careful monitoring of patients in a multidisciplinary care setting, and appropriate adjustments of treatment, is essential throughout pregnancy and the puerperium. In this special report we summarize best practice in the management of thyroid dysfunction in pregnancy.

Dissimilar hepatotoxicity profiles of propylthiouracil and methimazole in children

BACKGROUND

The antithyroid drugs propylthiouracil and methimazole were introduced for clinical use about 60 yr ago and are estimated to be used in more than 6000 children and adolescents per year in the United States. Over the years that these medications have been used, reports of adverse events involving hepatotoxicity have appeared. To date, there has not been a systematic and comparative evaluation of the adverse events associated with antithyroid drug use.

OBJECTIVE

Our objective was to assess safety and hepatotoxicity profiles of propylthiouracil and methimazole by age in the U.S. Food and Drug Administration's Adverse Event Reporting System (AERS).

DESIGN

We used the multi-item gamma-Poisson shrinker (MGPS) data mining algorithm to analyze more than 40 yr of safety data in AERS. MGPS uses a Bayesian model to calculate adjusted observed to expected ratios [empiric Bayes geometric mean (EBGM) values] for every drug-adverse event combination in AERS, focusing on hepatotoxicity events.

RESULTS

MGPS identified higher-than-expected reporting of severe liver injury in pediatric patients treated with propylthiouracil but not with methimazole. Propylthiouracil had a high adjusted reporting ratio for severe liver injury (EBGM 17; 90% confidence interval = 11.5-24.1) in the group less than 17 yr old. The highest EBGM values for methimazole were with mild liver injury in the group 61 yr and older [EBGM 4.8 (3.3-6.8)], which consisted of cholestasis. Vasculitis was also observed for propylthiouracil in children and adolescents, reaching higher EBGM values than hepatotoxicity signals.

CONCLUSIONS

MGPS detects higher-than-expected reporting of severe hepatotoxicity and vasculitis in children and adolescents with propylthiouracil but not with methimazole.

Shifts in propylthiouracil and methimazole prescribing practices: antithyroid drug use in the United States from 1991 to 2008

CONTEXT

The thionamide antithyroid drugs methimazole and propylthiouracil are the mainstay of pharmacologic therapy for Graves' disease. However, little is known about the rate of use of these drugs and the prescribing practices of physicians treating hyperthyroidism.

OBJECTIVE

The objective of the study was to examine the frequency of methimazole and propylthiouracil use from years 1991 to 2008.

METHODS

The data were acquired by the U.S. Food and Drug Administration's Division of Epidemiology through two databases: IMS National Sales Perspectives and the Surveillance Data, Inc. Vector One: National database.

RESULTS

There was a 9-fold increase in the annual number of methimazole prescriptions during the study period, from 158,000 to 1.36 million per year. There was a 19% increase in the annual number of propylthiouracil prescriptions, from 348,000 to 415,000 per year. Propylthiouracil, which held two thirds of the market from 1991 to 1995, was surpassed by methimazole in 1996. Patient demographic data indicated that although 72% of methimazole prescriptions were for females, males were more likely to be on methimazole (82%) than females (74%) (P < 0.001, two tailed chi(2) test). The only demographic group in which methimazole use decreased was women of child-bearing age (5% decrease, P < 0.001, two tailed chi(2)). The incidence of hyperthyroidism in 2008 was estimated based on the number of new prescriptions of thionamides by age group and data from the 2008 U.S. census: 0.44 per 1000 for ages 0-11 yr, 0.26 per 1000 for ages 12-17 yr, 0.59 per 1000 for ages 18-44 yr, 0.78 per 1000 for ages 45-64 yr, and 1.01 per 1000 for ages 65+ yr.

CONCLUSIONS

Methimazole has become the most frequently prescribed antithyroid drug. The remarkable increase in the total number of dispensed thionamide prescriptions over the last 18 yr may indicate a trend toward pharmacological treatment as primary treatment of Graves' disease in the United States.

Graves hyperthyroidism and pregnancy: a clinical update

OBJECTIVE

To provide a clinical update on Graves' hyperthyroidism and pregnancy with a focus on treatment with antithyroid drugs.

METHODS

We searched the English-language literature for studies published between 1929 and 2009 related to management of hyperthyroidism in pregnancy. In this review, we discuss differential diagnosis of hyperthyroidism, management, importance of early diagnosis, and importance of achieving proper control to avoid maternal and fetal complications.

RESULTS

Diagnosing hyperthyroidism during pregnancy can be challenging because many of the signs and symptoms are similar to normal physiologic changes that occur in pregnancy. Patients with Graves disease require prompt treatment with antithyroid drugs and should undergo frequent monitoring for signs of fetal and maternal hyperthyroidism and hypothyroidism. Rates of maternal and perinatal complications are directly related to control of hyperthyroidism in the mother. Thyroid receptor antibodies should be assessed in all women with hyperthyroidism to help predict and reduce the risk of fetal or neonatal hyperthyroidism or hypothyroidism. The maternal thyroxine level should be kept in the upper third of the reference range or just above normal, using the lowest possible antithyroid drug dosage. Hyperthyroidism may recur in the postpartum period as Graves disease or postpartum thyroiditis; thus, it is prudent to evaluate thyroid function 6 weeks after delivery. Preconception counseling, a multidisciplinary approach to care, and patient education regarding potential maternal and fetal complications that can occur with different types of treatment are important.

CONCLUSION

Preconception counseling and a multifaceted approach to care by the endocrinologist and the obstetric team are imperative for a successful pregnancy in women with Graves hyperthyroidism.

[Update hyperthyreoidism]

Hyperthyroidism is mainly caused by Graves' disease and toxic adenoma or multinodular goiter. In Europe, treatment of both disorders is usually started with antithyroidal drugs such as methimazole. Complications include agranulocytosis and the risk is dose-dependent. The starting dose of methimazole should not exceed 15-20 mg/d. Propylthiouracil can cause severe liver failure, leading to liver transplantation or death. Propylthiouracil, therefore, should not be used as first line agent and is only recommended when an antithyroid drug is to be started during the first trimester of pregnancy or in individuals who have experienced adverse responses to methimazole. Toxic adenoma is finally treated with radioioidine. To reduce the risk of treatment failure, antithyroidal drugs should be stopped at least one week prior to radioiodine. For Graves' disease, remission is unlikely if antibodies against the TSH-receptor remain above 10 mU/l after 6 months of antithyroidal treatment and radioiodine or thyroidectomy can be recommended. Thyroidectomy should be performed as (near) total thyreoidectomy.

Adverse events associated with methimazole therapy of graves' disease in children

Objective. Graves' disease is the most common cause of hyperthyroidism in the pediatric population. Antithyroid medications used in children and adults include propylthiouracil (PTU) and methimazole (MMI). At our center we have routinely used MMI for Graves' disease therapy. Our goals are to provide insights into adverse events that can be associated with MMI use. Methods. We reviewed the adverse events associated with MMI use in our last one hundred consecutive pediatric patients treated with this medication. Results. The range in the patient age was 3.5 to 18 years. The patients were treated with an average daily dose of MMI of 0.3+/-0.2 mg/kg/day. Adverse events attributed to the use of the medication were seen in 19 patients at 17+/-7 weeks of therapy. The most common side effects included pruritus and hives, which were seen in 8 patients. Three patients developed diffuse arthralgia and joint pain. Two patients developed neutropenia. Three patients developed Stevens-Johnson syndrome, requiring hospitalization in 1 child. Cholestatic jaundice was observed in 1 patient. No specific risk-factors for the development of adverse events were identified. Conclusions. MMI use in children is associated with a low but real risk of minor and major side effects.

Propylthiouracil-induced acute liver failure: role of liver transplantation

Propylthiouracil- (PTU-) induced hepatotoxicity is rare but potentially lethal with a spectrum of liver injury ranging from asymptomatic elevation of transaminases to fulminant hepatic failure and death. We describe two cases of acute hepatic failure due to PTU that required liver transplantation. Differences in the clinical presentation, histological characteristics, and posttransplant management are described as well as alternative therapeutic options. Frequent monitoring for PTU-induced hepatic dysfunction is strongly advised because timely discontinuation of this drug and implementation of noninvasive therapeutic interventions may prevent progression to liver failure or even death.