Apathetic Hyperthyroidism with Heart Failure in an Elderly Patient with Plummerʼs Disease

We report a case of apathetic hyperthyroidism associated with unrecognized slowly growing functional thyroid adenoma (Plummer's disease), atrial fibrillation and heart failure. An 81-year-old woman with worsening thyroid dysfunction was admitted to our hospital for the treatment of heart failure. The patient had developed heart failure associated with chronic atrial fibrillation at 76 years of age, and one year later was found to have asymptomatic hyperthyroidism. Anti-thyroid autoantibodies were negative, but thyroid echography showed a 32-mm tumor devoid of internal blood flow in the left lower lobe. Free thyroxine 4 (FT4) decreased from 3.30 to 2.60 ng/dl without treatment. The patient was diagnosed with transient thyroiditis and was followed-up without treatment. However, a repeat thyroid echography showed growth of the tumor to 41 mm in 4 years. Thyroid scintigraphy showed uptake that matched the thyroid mass. Based on these findings, the established diagnosis was Plummer's disease complicated with heart failure. The patient was treated with anti-thyroid drugs, which resulted in improvement of FT4 and reduced the severity of heart failure. In this rare case of an elderly patient, Plummer's disease was associated with a slowly-growing functional thyroid adenoma, apathetic hyperthyroidism, repeated episodes of atrial fibrillation and heart failure. Since symptoms of thyrotoxicosis are likely to be missed in the elderly, it is necessary to include hyperthyroidism in the pathoetiology of heart failure and atrial fibrillation in this population.