Circadian rhythms in adrenocortical adrenocortical activity during and after a 36 hour 4-hourly-sustained administration of metyrapone in humans

Abstract

The circadian variations of plasma cortisol, plasma 11-deoxycortisol and their urinary metabolites, 17-hydroxycorticosteroids and tetrahydro-11-deoxycortisol, have been investigated on two healthy young human males before, during and after a 36 h sustained oral administration of metyrapone (total dose: 7.50 g). Circadian changes were analysed by the cosinor method. Subjects were synchronized with diurnal activities from 0715 h to 2300 h and nocturnal rest. A circadian rhythm is likely to be present for plasma cortisol before, and plasma 11-deoxycortisol after metyrapone administration. A prominent peak has been shown at a trial period of 24 h. A circadian rhythm seems to be present in 17-hydroxycorticosteroids excretion before during and after metyrapone administration. In tetrahydro-11-deoxycortisol excretion it was found only during and after, and in the estimated portion of 11-hydroxylated tetrahydrocorticosteroids before and after, but not during metyrapone administration. The acrophases of validated rhythms in urinary steroids are located between 1130 h and 1630 h.