Relationship between plasma renin and cortisol in hypertensive patients.

1. Plasma cortisol at 08.00 hours was significantly higher (P less than 0.005) in patients with high-renin essential or renovascular hypertension (22.6 +/- 1.6 microgram/100 ml) than in patients with normal-renin (15.4 +/- 1.2) or low-renin (11.9 +/- 1.2) forms of hypertension. 2. Plasma cortisol at 12.00 or 16.00 hours did not differ significantly among the three groups; thus the diurnal swing in plasma cortisol was steepest in patients with high plasma renin. 3. Among all patients studied, there was a direct relationship between 08.00 hours plasma cortisol and ambulatory plasma renin activity (r = 0.65, P less than 0.001). 4. In patients with high-renin values, 08.00 hours plasma cortisol fell by 39 +/- 6% after 10 days treatment with the converting enzyme inhibitor captopril. No consistent decreases were observed in the normal- or low-renin groups. 5. We conclude that the renin--angiotensin system may interact with the pituitary--adrenal axis to influence circulating levels of cortisol. This effect might conceivably contribute to the pathogenesis of certain high-renin states.