The significance of changes in plasma cortisol concentration and renal excretion of corticosteroids after a water load.

Abstract

SUMMARY 1. Plasma cortisol concentrations, and the urinary output of free and conjugated Porter-Silber reacting steroids, 17-ketosteroids (17-KS), 'total 17-OH CS', urinary cortisone and cortisol, free and conjugated tetrahydrocortisone and cortisol were measured before and after a 1 l. water load. 2. The plasma cortisol concentration fell within 30 min of water ingestion, and tended to increase as diuresis declined. 3. There was a simultaneous increase in the urinary output of 17-KS, total 17-OH CS, and free Porter-Silber reacting steroids. In contrast, urinary excretion of glucuronide-conjugated corticosteroids did not increase during diuresis. 4. The implications of these findings are discussed and it is concluded that (a) the enhanced corticosteroid output during water diuresis is renal in origin, suggesting that tubular factors play a part in the excretion of these hormones; and (b) the role of the adrenal in the excretion of a water load is permissive.