Thyroid hormone abnormalities in heart failure: possibilities for therapy

Though thyroid hormone abnormalities have been identified in many cardiac conditions, the role of thyroid hormones in congestive heart failure has not been well defined. In a population of patients with advanced heart failure, a reduction in triiodothyronine (T3) with an increase in reverse T3 was identified in many patients, with an abnormally low ratio of T3/reverse T3 being the strongest predictor of mortality. Normalization of thyroid indices appeared to be necessary for prolonged survival to occur. To address the concern of T3 administration possibility exacerbating a hypermetabolic state, basal metabolic rate was measured in a group of advanced heart failure patients and was found to be generally within the normal range. A preliminary safety study of short-term intravenous T3 administration (bolus +/- 6 h infusion, total dose 0.15-2.7 micrograms/kg) was then performed in 23 patients under hemodynamic and electrocardiographic monitoring. There were neither adverse events nor substantial hemodynamic changes, but some patients had an increase in cardiac output, consistent with a peripheral vasodilatory effect. With this foundation, further investigation into the possible role of T3 and its analogs in congestive heart failure therapy may be pursued.