Endocrine Abstracts

Background: Amiodarone is a commonly used antiarrhythmic drug, but because of its abundance with iodine and a direct toxic effect on the thyroid, it can have side effects like hypo- and hyperthyroidism. There are two types of amiodarone-induced thyrotoxicosis (AIT). We present a case which demonstrates the importance of timely diagnosis and appropriate treatment of amiodarone-induced thyrotoxicosis in patients with serious cardiac comorbidities.

Case Presentation: A 74-year-old male with a history of multinodular goiter, hypertension, paroxysmal atrial fibrillation, implanted mechanical aortic valve because of aortic regurgitation, left ventricular hypertrophy, and reduced ejection fraction was referred to our clinic because of hyperthyroidism. Four months prior to this visit, amiodarone was discontinued by his cardiologist after five years of use. At that time, the patient had a thyroid stimulating hormone (TSH) level below the lower reference limit and no hypermetabolic symptoms. No thyrostatic treatment was initiated nor was he referred to an endocrinologist. Two months later, the patient developed symptoms of hyperthyroidism; TSH was suppressed. His primary care physician started him on 10 mg of thiamazole daily. After two more months, the patient’s state worsened. He was referred to an otorhinolaryngologist. Urgent restoration of stable clinical state was needed because the patient had cardiac decompensation and overt hyperthyroidism with suppressed TSH and high free thyroxine (FT4) level, as well as prolonged prothrombin time due to coumarin use. After cardiac recompensation, normalization of the coagulogram, and reduction of the FT4 level under full thiamazole dose (which stayed slightly above the upper reference limit), thyroidectomy was performed. Significant clinical and laboratory improvement followed.

Conclusions: AIT has been associated with increased morbidity and mortality, especially in older patients with impaired left ventricular function. The importance of rapid recovery and stable maintenance of euthyroidism should be emphasized to both endocrinologists and non-endocrinologists.