Fulminant hepatitis after carbimazole and propranolol administration

The interplay between thyroid and liver: implications for clinical practice

A complex relationship exists between thyroid and liver in health and disease. Liver plays an essential physiological role in thyroid hormone activation and inactivation, transport, and metabolism. Conversely, thyroid hormones affect activities of hepatocytes and hepatic metabolism. Serum liver enzyme abnormalities observed in hypothyroidism may be related to impaired lipid metabolism, hepatic steatosis or hypothyroidism-induced myopathy. Severe hypothyroidism may have biochemical and clinical features, such as hyperammonemia and ascites, mimicking those of liver failure. Liver function tests are frequently abnormal also in hyperthyroidism, due to oxidative stress, cholestasis, or enhanced osteoblastic activity. Antithyroid drug-associated hepatotoxicity is a rare event, likely related mainly to an idiosyncratic mechanism, ranging from a mild hepatocellular damage to liver failure. Propylthiouracil-induced liver damage is usually more severe than that caused by methimazole. On the other hand, thyroid abnormalities can be found in liver diseases, such as chronic hepatitis C, liver cirrhosis, hepatocellular carcinoma, and cholangiocarcinoma. In particular, autoimmune thyroid diseases are frequently found in patients with hepatitis C virus infection. These patients, especially if thyroid autoimmunity preexists, are at risk of hypothyroidism or, less frequently, thyrotoxicosis, during and after treatment with interpheron-alpha alone or in combination with ribavirin, commonly used before the introduction of new antiviral drugs. The present review summarizes both liver abnormalities related to thyroid disorders and their treatment, and thyroid abnormalities related to liver diseases and their treatment.

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.

A Case of Propylthiouracil-Induced Hepatitis during Pregnancy

A 32-year-old with no pre-existing liver disease was diagnosed with Graves' disease at week 4 of pregnancy. Thyroid-stimulating hormone was undetectable with elevated free thyroxine levels and positive thyroid receptor antibodies. She was started on a reducing regime of propylthiouracil (PTU). At week 20 in pregnancy, she became jaundiced. Initial bloods revealed: bilirubin 91 μmol/l, alanine aminotransferase 1,796 IU/l, alkaline phosphatase 200 IU/l, international normalized ratio 1.2, and albumin 33 g/l. A presumptive diagnosis of PTU-induced hepatitis was made. PTU was immediately discontinued and best supportive care instigated. Serum markers for autoimmune and viral hepatitis were negative, abdomen ultrasound, ferritin and caeruloplasmin were normal. Although her alanine aminotransferase began to fall, her bilirubin continued to rise, peaking at 378. Two weeks after PTU cessation she became thyrotoxic and was started on a reducing regime of carbimazole. Her thyroid function stabilized and liver function tests continued to improve with carbimazole stopped at week 32. Growth scans remained normal with delivery of a healthy baby at 38 weeks. This report highlights that good outcomes can be achieved in PTU-induced hepatitis in pregnancy. Patients on PTU should be warned of the potential risk of hepatic failure and advised to seek medical advice immediately if they develop jaundice.

Methimazole-induced Cholestatic Jaundice

Methimazole is a widely used and generally well-tolerated antithyroid agent. A 43-year-old woman had severe jaundice and itching 1 month after receiving methimazole (10 mg tid) and propranolol (20 mg tid) for treatment of hyperthyroidism. The patient continued treatment for another 4 days after the appearance of jaundice until she finished both medications. When seen at the emergency department 2 weeks later, she still had severe icterus, pruritus, and hyperbilirubinemia, formed mainly of the conjugated fraction. Methimazole-induced cholestasis was diagnosed, and propranolol therapy was resumed. Over the following 9 days, the symptoms improved and plasma bilirubin levels were normal after 12 weeks without methimazole. In rare cases within the first few weeks of therapy, this drug can cause severe and reversible cholestatic jaundice. Physicians and patients should be aware of this adverse effect so that, upon occurrence, they can discontinue methimazole therapy and avoid unnecessary invasive procedures.

Acute liver failure with concurrent bupropion and carbimazole therapy

OBJECTIVE

To report a case of fatal liver failure possibly associated with concurrent use of bupropion and carbimazole.

CASE SUMMARY

A 41-year-old Chinese man with a history of hyperthyroidism had been treated with carbimazole and propranolol for the past 5 years. He received a 10-day course of bupropion as an aid for smoking cessation 10 weeks prior to presentation. He developed acute liver failure with rapid deterioration of renal function. Liver biopsy showed evidence of nonspecific drug-induced acute liver injury. His condition was further complicated by sepsis and coagulopathy. Death resulted 19 days after the onset of symptoms. The likelihood that bupropion induced hepatotoxicity in our patient was possible, based on the Naranjo probability scale.

DISCUSSION

Although there is increasing evidence of hepatotoxicity induced by bupropion, this is the first case of fatality that could have resulted from acute liver failure in a patient receiving bupropion while on concomitant treatment with carbimazole.

CONCLUSIONS

Clinicians should be aware of the possibility of acute liver insult induced by bupropion given concurrently with other hepatotoxic drugs.

Methimazole-induced hepatotoxicity

OBJECTIVE

To present the case of a patient with Graves' hyperthyroidism in whom treatment with methimazole led to severe cholestasis.

METHODS

A detailed case report and an overview of previously published cases of methimazole- and carbimazole-induced hepatotoxicity, found in a MEDLINE search with use of methimazole, carbimazole, thionamides and antithyroid agents as subject headings, are provided.

RESULTS

In a 36-year-old woman with severe hyperthyroidism, treatment with methimazole (20 mg twice daily) was initiated. Nineteen days later, pruritus, scleral icterus, dark urine, and abdominal discomfort prompted discontinuation of the therapy. Laboratory investigations and abdominal ultrasonography showed findings consistent with a cholestatic reaction to methimazole. Recovery was slow but complete. Of the 30 previously published cases of hepatotoxicity related to treatment with methimazole or carbimazole in which the nature of the hepatic injury was described, 19 were also cholestatic.

CONCLUSION

Physicians should be aware that thionamide drugs can be associated with hepatotoxicity. Analysis of the known cases suggests that older age of the patient and higher dose of the drug are risk factors for cholestatic injury.