6 beta-hydroxycortisol in random urine samples as an indicator of enzyme induction.

6 beta-Hydroxycortisol (6 beta-OHF) is a major cortisol metabolite formed primarily in the hepatic reticulum by mixed-function oxygenases. Changes in 6 beta-OHF may be used to detect enzyme induction by drugs or disease. Excretion of 6 beta-OHF must be corrected for change in urinary free cortisol (FF) excretion to allow for changes in cortisol production. We report the absence of circadian changes in 6 beta-OHF/FF ratios. Thus random measurements of 6 beta-OHF/FF ratios may be used to detect enzyme induction. This approach greatly simplifies noninvasive screening for enzyme induction.