[State of the renin-angiotensin system in thyrotoxicosis]

A study was made of the blood plasma renin activity in 63 patients suffering from thyrotoxicosis before the treatment and in 42 healthy individuals. In comparison with the healthy, renin activity was increased in patients with thyrotoxicosis and displayed a positive correlation with the severity of the disease the level of protein-bound iodine, tachycardia and the degree of loss of weight. Stimulation of the renin-angiotensin system by the salt-free diet, hydrochlorthiazide and by placing the body into orthostatic position caused a relatively weaker increase in the renin activity in comparison with such in healthy individuals. Following successful treatment and the occurrence of an euthyroidal state renin activity proved to fall to the normal level. An increased renin activity was combined with increased urinary aldosterone excretion with a normal serum electrolyte level. Such combination pointed to the secondary character of aldosteronism. Block of the alpha- and beta-adrenergic receptors led to reduction in the level of renin activity. Despite the frequent affection of hepatic function there was revealed no correlation between the increase in the renin activity and the pathological results of hepatic tests. Plasma renin activity was reduced in 8 patients with myxedema. It is supposed that the principal factors causing activation of the renin-angiotensin system in thyrotoxicosis were the loss of water and electrolytes by the organism and the appearance of oversensitivity to adrenergic receptors.