Abstract

Some of the symptoms and signs of hyperthyroidism are caused by increased sensitivity of tissues to sympathetic activity. Sympathetic effects mediated by β-receptors, such as the cardiac and peripheral vasodilator effects, seem to be especially prominent in hyperthyroidism. Exaggerated circulatory responses to injected adrenaline and noradrenaline have been demonstrated in hyperthyroid patients;¹ there is no evidence that excess thyroid hormone increases plasma or tissue levels of these catecholamines.