Studies of the Diurnal Variation of Plasma 17-Hydroxycorticosteroids in Man*

Studies are reported of the diurnal variation of plasma 17-OHCS concentration in normal subjects and in patients with various diseases. Only in clinical situations associated with alterations in consciousness or sleep pattern was there significant loss of the diurnal rhythm. The rate of removal of hydrocortisone from the plasma was the same at various times of the day, but the adrenal production of 17-OHCS in response to maximally stimulating doses of ACTH was less at night than at other times during the 24-hour period. Submaximal stimulation of the adrenal cortex with ACTH during the late afternoon and evening restored to normal the nocturnal adrenal response to ACTH. It is suggested that the diurnal variation of plasma 17-OHCS depends on variations in the rate of secretion of ACTH. The change in ACTH secretion apparently is controlled by a central nervous system mechanism of unknown character. Total reversal of sleep and activity in normal subjects results in reversal of the diurnal rhythm in plasma 17-OHCS and serum iron levels, and body temperature.