Subclinical Hyperthyroidism

This Journal feature begins with a case vignette highlighting a common clinical problem. Evidence supporting various strategies is then presented, followed by a review of formal guidelines, when they exist. The article ends with the author's clinical recommendations. A 67-year-old woman presents with palpitations and is found to be in atrial fibrillation at a rate of 120 beats per minute. The only other finding on physical examination is a goiter, which is known to be long-standing. Echocardiography shows neither valvular disease nor left ventricular systolic dysfunction. The serum thyrotropin concentration is less than 0.05 mU per liter, and the serum total triiodothyronine and free thyroxine concentrations are in the normal range. Should the thyroid dysfunction be treated?The Clinical ProblemThe combination of an undetectable serum thyrotropin concentration, as measured by an assay with a threshold of . . .