Diurnal Variation of Plasma Aldosterone, Cortisol and Renin Activity in Supine Man

Abstract

In order to evaluate episodic secretion of aldosterone over the entire day, plasma aldosterone, renin activity and cortisol were measured every 10 or 30 min in normal human subjects, on both normal and sodium restricted diets, while receiving dexamethasone, on oral contraceptives and in patients with primary aldosteronism, all while supine. Peak levels of aldosterone occurred in the latter part of the sleeping hours and early in themorning in normal subjects on normal sodium diets. Aldosterone was positively correlated with cortisol in all these subjects but with renin in only 3 out of 5. When cortisol secretion was suppressed by dexamethasone, the hours of peak plasma aldosterone levels were the same, and these peak levels were not always related to renin. These data are compatible with a common determinant for ACTH and aldosterone secretion rhythms in supine man. On sodium restriction both subjects tested hadstatistically significant correlation of aldosterone with both cortisol and renin, and the 2 women onoral contraceptives demonstrated varying patterns of correlation. Patients with primary aldosteronism had either constantly high levels above the normal range or secretory spurts synchronous with cortisol. One of the patients given dexamethasone had no change in his secretion.