Significant reversal of thyrotoxicosis-associated dilated cardiomyopathy with induction of the euthyroid state.

Thyrotoxicosis rarely precipitates heart failure. Older patients and those with underlying cardiac disease are at greater risk of experiencing this complication of thyrotoxicosis. A 43 year old male who presented with subclinical thyrotoxicosis, atrial fibrillation, and a dilated cardiomyopathy is discussed. There was no evidence of clinically significant underlying cardiac disease. At admission, the patient had an ejection fraction of 25%. Thyrotoxicosis was treated with propylthiouracil. At 14 weeks after hospitalization, the patient had an ejection fraction of 50% with significant reduction in cardiac chamber sizes and left ventricular mass index. He was biochemically euthyroid at that time. After ten months of propylthiouracil therapy, he had progressive improvement in cardiac function and decrease in left ventricular mass index. Thyrotoxicosis-associated cardiomyopathy may reverse significantly with treatment of thyrotoxicosis alone; this complication of thyrotoxicosis should be considered in any young individual with a dilated cardiomyopathy of unknown etiology.