THYROID-FUNCTION IN DOGS WITH SPONTANEOUS AND INDUCED CONGESTIVE-HEART-FAILURE

The effects of spontaneous and experimentally induced congestive heart failure on serum thyroxine (T4), 3,5,3'-triiodothyronine (T3), 3,3'5' -triiodothyronine (reverse T3), free T4, free T3 concentrations, and t he serum T4 and T3 concentrations in response to administration of thy rotropin were studied. Serum thyroid hormone concentrations were not d ifferent between eight dogs with spontaneous congestive heart failure and normal age matched control dogs. Seven dogs with experimental hear t failure were tested before and after induction of congestive heart f ailure by rapid ventricular pacing. Mean serum Til and free T3 concent rations were decreased and mean serum reverse T3 concentration was inc reased following induction of heart failure. The serum T4 and T3 respo nses to thyrotropin were not altered. Thyroid gland morphology appeare d normal in dogs with experimental heart failure. Experimental congest ive heart failure, similar to some other nonthyroidal illnesses, alter s thyroid hormone secretion and metabolism in dogs.