Antithyroid Drug-Induced Hepatotoxicity From Chronic Methimazole Consumption Requiring Total Thyroidectomy

Antithyroid drug-induced hepatotoxicity is extremely rare with very few reported cases in the literature. The typical presentation of antithyroid drug-induced hepatotoxicity is acute onset of symptoms from high dose antithyroid medications in middle-aged females. Here we present an 82-year-old male with a 1-month history of jaundice, scleral icterus, choluria, and fatigue. He has a past medical history of Graves’ disease treated with 5 mg methimazole for 6 years. After extensive laboratory and imaging work up from a multi systems specialty approach, the patient was found to have cholestatic liver cirrhosis. Further ruling out benign, malignant, autoimmune, surgical, other pharmacological, or social causes of this cholestatic liver disease we concluded that the patient had hepatotoxicity secondary to methimazole. The patient successfully underwent total thyroidectomy with subsequent levothyroxine supplementation. Pathology was consistent with a normal sized thyroid with parenchymal fibrosis with lymphocytic infiltrates consistent with medically treated Graves’ disease. Post-operatively the patient’s hepatic function is normalizing.