KINETIC ASPECTS OF CORTISOL-4-C14 METABOLISM IN A PATIENT AFTER SUBTOTAL ADRENALECTOMY FOR CUSHING'S SYNDROME ASSOCIATED WITH BILATERAL ADRENAL HYPERPLASIA*

Abstract

Cortisol half-lives, turnover, metabolite pool sizes, and rates of formation of metabolites were obtained in this 23-year-old woman on two occasions during which cortisol tunover was fixed by continuous infusion at 200 mg per 24 hours. After 16 hours a small amount of cortisol-4-c14 was administered and from urine samples collected every 15 minutes for 8 hours specific activities of cortisol and its metabolites were determined. Pool sizes were calculated by isotope dilution after aministration of unlabeled metabolite. Cortisol turnover calculated from both first-order cortisol specific activity curves and from the integral specific activity curves of the metabolites allo-THF and 6B-hydroxycortisol agreed with the fixed infusion rate. Amounts of THF and THE excreted were directly proportional to their pool sizes. Allo-THF pools were very small. Rates of formation of THF, allo-THF, and THE computed from the kinetic data as well as the recovery of this group of metabolites from urine approximated only 50 per cent of the turnover of cortisol.