Endocrine Abstracts

Introduction: Methimazole is a widely prescribed antithyroid drug for the treatment of hyperthyroidism with a few adverse effects generally well-tolerated. However, methimazole-induced cholestatic jaundice (CJ) is a rare but serious adverse reaction. Herein we report a rare case of methimazole-induced CJ in a woman with hyperthyroidism.

Case report: A 57-years-old women presented to our endocrinology department with a 2-week history of asthenia, insomnia, tremulousness, and swollen eyes. On Physical examination she had a body weight of 69 kg, a body mass index of 23 kg/m², a blood pressure of 130/70 mm Hg and a pulse rate of 100 beats per minute. The neck examination revealed a homogenic and elastic goiter with a thrill. The eye examination showed bilateral and symmetric upper eyelid retraction, swelling and grade 1 exophtalmos. Laboratory tests showed hyperthyroidism with a low TSH of 0.006 μIU/ml and elevated freeT4 of 52.36 ng/l(9-17). The liver enzymes were normal. The ultrasound of the thyroid revealed a diffuse micronodular and hypervascular thyroid gland. Thyroid scintigraphy showed homogenous increased uptake of the thyroid gland. She was started on methimazole 30 mg a day and propranolol 10 mg three times a day. Six weeks later, she returned with severe jaundice, pruritus, dark urine and light-colored stool. The clinical findings showed a severe icterus. Physical examination of the abdomen, heart, liver, and spleen were unremarkable. She had neither fever nor signs of chronic liver disease. Initial tests were consistent with a CJ: elevated alanine aminotransferase 168 U/l (10-45), aspartate aminotransferase 213 U/l (10-40), gamma glutamyl transferase 129 u/l (7-50) and significantly elevated alkaline phosphatase 952 U/l (35-104), total bilirubin 321 mg/dl (5-17), conjugated bilirubin 319 mg/dl (2-5). The prothrombin time was normal. The hepatobiliary ultrasonography excluded biliary obstruction. The viral hepatitis, autoimmune hepatitis and primary biliary cirrhosis were also ruled out. Cholestatic jaundice due to methimazole was very likely. The medication was discontinued immediately. The patient was started on prednisone 1 mg/kg/day. The recovery was slow but complete after 7 weeks of methimazole withdrawal. She was then referred for iodine radiation treatment.

Conclusion: We discuss this case to study the rare association between methimazole use and cholestatic jaundice. This drug can cause severe but reversible CJ. Thus, physicians and patients should be aware of this adverse effect so that they can discontinue methimazole therapy upon the occurrence.