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Two normal men had blood taken for measurement of plasma aldosterone, cortisol and renin activity every 30 minutes while supine for 24 hours. Aldosterone secretion occurred in spurts as is true for cortisol. Moreover, peak levels for these two adrenal hormones were synchronous during late sleep and on arising, as was renin activity frequently. However cortisol peaks later in the day were not synchronous with aldosterone.The adrenocortical secretion of. cortisol and dehydroisoandrosteronein normal subjects (1) and of cortisol in Cushing's disease (2) has recently been shown to be episodic over the period of a day, with substantial portions of the day quiescent of secretion. Moreover, frequent sampling of bl,ood levels showed that these two adrenal hormones, from the zona fasciculata and reticularis respectively, appear to be secreted synchronously. We have measured the plasma concentration of the hormone of the zona glomerulosa, aldosterone, at frequent intervals, together with plasma cortisol and plasma renin activity. These studies show that aldosterone too is secreted in bursts and that, in supine man, they are synchronous with those of cortisol which occur during late sleep and early after arising, and thus perhaps dependent on ACTH secretion (3). MATERIALS AND METHODSTwo normal men, P.R., a 26 year old student, and M.K., a 27 year old physician, were given diets containing 130 meq Na and 70 meq K per day for 5 days on the metabolic ward. Urinary electrolytes confirmed adherence to the diet. The subjects slept in the hospital the night before being studied. During the last 26 hours of the 5 day period they remained supine in bed, except for brief periods up to the bathroom for less than 5

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A post-ovulatory peak of fasting supine plasma aldosterone (PA) preceded or accompanied by an increase in plasma renin activity (PRA) was previously reported. These studies have now been extended in 4 additional normal menstruating women and 4 women taking oestrogen\x=req-\ progestogen oral contraceptive pills (OCP), all studied daily for an entire cycle. Distinct luteal phase increases in PRA were seen in the 4 normals, with 2 also demonstrating a rise in PA. Plasma renin substrate (PRS) was usually unvarying throughout the control cycles. The women taking OCP, on the other hand, all had PA and PRA peaks that were apparent by the fourth or fifth day of taking "the pill". All 4 of the treated women had elevated PRS levels but only one woman showed an increase which preceded the elevation of PRA and PA. Plasma cortisol levels were usually above the normal range in the women taking OCP. This study thus indicates that factors other than oestrogen-induced increased substrate production may be responsible for the PRA and PA rise during OCP treatment Such factors might be the natri-uretic effects of oestrogens and progestogens or a direct effect on renin secretion by one of these steroids.

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