Circadian rhythm of urinary 17-hydroxycorticosteroids during metyrapone-induced ACTH release in normal subjects.

The circadian rhythm of urinary 17-OHCS was studied in nine normal subjects before and after oral metyrapone administration (750 mg every 4 hrs over a period of 24 hrs). The test was carried out twice in each subject with a shift of 12 hrs in the time of first administration (0800-test and 2000-test). For data from serial measurements of steroid metabolites on urine collected at 2-h intervals, the least squares fit of a 24-h cosine curve allowed the demonstration of a rhythm both in control conditions and during the 48-h span following metyrapone administration.