[Estimation of free cortisol in urine (author's transl)]

Radio-immunological estimation of free cortisol in urine in a group of normal persons showed a median daily excretion of 42,5 +/- 22,8 mug (n = 31) using radio-loss-labelling, extraction, and thin layer chromatography. After simple extraction the median value was 54.1 +/- 15.3 mug/d (n = 10). Radioimmunological estimation in simple urine extract seems to be sufficient for routine clinical purposes. The estimation of free cortisol in urine permits a better differentiation between normal adrenal function and adrenal hyperactivity than the determination of 17-hydroxycorticosteroids (17-OHCS). This is shown by comparison of 1) the frequency distribution of the basal values of 17-OHCS and free cortisol in normal persons and in Cushing's disease, 2) the suppression effect of dexamethasone on 17-OHCS and free cortisol in Cushing patients, and 3) the stimulatory effect of ACTH on 17-OHCS and free cortisol in normal persons.