CIRCADIAN-RHYTHM OF URINARY 17-HYDROXYCORTICOSTEROIDS DURING METYRAPONE-INDUCED ACTH RELEASE IN NORMAL SUBJECTS

  • 1 January 1975
    • journal article
    • research article
    • Vol. 2  (2) , 133-144
Abstract
The circadian rythm of urinary 17-hydroxycorticosteroids (17-OHCS) was studied in 9 normal subjects before and after oral metyrapone administration (750 mg every 4 h over a period of 24 h). The test was carried out twice in each subject with a shift of 12 h in the time of 1st administration (0800-test and 2000-test). From serial measurements of steroid metabolites on urine collected at 2-h intervals, the method of least squares for a 24-h cosine curve showed a rhythm both in control conditions and during the 48-h span following metyrapone administration. Circadian acrophases were similar. Total urinary 17-OHCS output in the first 24-h day following metyrapone was higher in the 2000 test as compared with the 0800-test (P < .001). Conversely, in the 2nd 24-h day, higher values were obtained in the 0800-test (P < .025). The combined 48-h excretion was identical in the 2 groups. A time-limited action of metyrapone upon the pituitary-adrenal axis is suggested, since the increased excretion of 17-OCHS seems essentially accounted for by an exaggerated impulsive phase of ACTH secretion during the early morning hours.