Amiodarone-Induced Thyrotoxicosis in a Patient with Multinodular Goiter

Abstract

An old male who presented with atypical symptoms was diagnosed with thyrotoxicosis. He had multinodular goiter and was taking amiodarone (probably intermittently for a long time) for atrioventricular arrhythmias. The findings were interpreted in favor of amiodarone thyroiditis, but it was difficult to distinguish the type of amiodarone-induced thyrotoxicosis (AIT) because findings of both type 1 and 2 AIT were observed. Combined antithyroid drug (methimazole 20 mg/day) and corticosteroid (prednisolone 40 mg/day) were administered to treat both types of AIT. Normal thyroid hormone levels were found in the second week of treatment. Hepatotoxicity and decreasing platelet count developed as side effects of methimazole; therefore, the drug was stopped. Prednisolone was continued at the same dosage for 4 weeks and tapered to 6–10 mg every 4 weeks. Meanwhile, liver enzyme levels and platelet count returned to acceptable levels, but there was a risk of exacerbation. The patient was operated during the fourth month of follow-up when his cardiac problems were stable.