The miscible pool and turnover rate of hydrocortisone in man.

In 1948, Mason and Sprague (1) reported the isolation of hydrocortisone from the urine of a patient with Cushing's syndrome, and thus provided evidence that hydrocortisone was produced by the human adrenal cortex. Subsequently, hydrocortisone was found to be one of the principal corticoids in human adrenal gland perfusates (2) and in human peripheral blood (3). These observations strongly suggest that hydrocortisone may be the principal corticosteroid secreted by the adrenal cortex of man. Recent studies (4, 5) utilizing hydrocortisone-4-Cli have elucidated much new information regarding the metabolism and physiological disposition in man of this naturally occurring adrenal steroid. The availability of labeled hydrocortisone has made possible the direct estimation of the magnitude of the reservoir of hydrocortisone in the body, and the rate at which new, non-isotopic hydrocortisone is synthesized in the body and enters the reservoir. This report is concerned with the experimental determination of the magnitude of the miscible pool of hydrocortisone and the rate of its turnover in man. These estimations depend upon serial measurements of the specific activity of circulating hydrocortisone after the infusion of trace quantities of hydrocortisone4-0C1 and analyses of these data utilizing conventional turnover calculations (6, 7). Observations have been made in normal subjects, and subjects receiving adrenocorticotropin and A1 cortisone (prednisone).