Effect of thyroid hormones on cardiovascular and muscle systems and on exercise tolerance: a brief review.

THYROID HORMONES AND THE CARDIOVASCULAR SYSTEM According to the classical literature on human physiology4, thyroid hormones – thyroxine (T4) and triiodothyronine (T3) – produce an overall increase in the basal metabolism of the human body. This is accompanied by greater tissue oxygen consumption, owing both to vasodilation and the concomitant increase in cardiac output, which are facilitated by enhanced chronotropism and inotropism. Studies of hyperthyroid patients5-10 have demonstrated that they show increased contractile force and cardiac output, with decreased peripheral resistance.