Atrial fibrillation due to late amiodarone-induced thyrotoxicosis.

A 60-year-old male patient complaining of palpitations, fatigue, weakness and weight loss of 1 month's duration was hospitalized in our cardiology department for atrial fibrillation. Thyroid function test results were compatible with thyrotoxicosis. The patient had been taking amiodarone for 2.5 years for hypertrophic obstructive cardiomyopathy and non-sustained ventricular tachycardia episodes. However, amiodarone had been discontinued after follow-up examinations revealed that the patient's ventricular arrhythmias were no longer present, and he had been taking metoprolol only for the preceding 6 months. In this patient, amiodarone-induced thyroiditis had developed 6 months after cessation of treatment, demonstrating that adverse effects may occur after discontinuation of amiodarone. Detection of the condition requires assessment of thyroid function before treatment initiation, during treatment and at regular intervals after treatment cessation. The type of hyperthyroidism induced by amiodarone cannot be determined in most cases. Patients with this condition should be referred to an experienced endocrinologist. Our case of delayed amiodarone-induced thryoiditis occcurred approximately 6 months after termination of amiodarone treatment.