Elucidation of Mechanism(s) of the Nocturnal Rise of Testosterone in Men

To elucidate the mechanism (s) responsible for the nocturnal rise of testosterone in men, 4 adult male subjects were studied for 3 nights at weekly intervals. On the third night each subject was given 2 mg of dexamethasone by mouth just before retiring. Sharp increases in the plasma testosterone (T), androstenedione (Δ) and dehydroepiandrosterone (dhea) levels were noted during the 8 control nights. Dexamethasone blocked the rise of DHEA, Δ, and cortisol, but not of testosterone. Fourteen distinct pulses of T (>15OO pg/ml) were observed. A discernible LH peak preceded 12 of the T pulses with a lag time of 20–140 min (median 80 min). Although rises of T were invariably preceded by LH peaks, one-third (12 of 36) of the LH peaks were followed by a distinct T elevation. No relationship was found between T elevations and the onset of sleep, REM sleep, or prolactin and FSH levels. These data suggest (1) plasma T, Δ, DHEA rise at night usually in episodic bursts; (2) the rise of T is testicular in origin, while the increase of Δ and DHEA comes from the adrenal; (3) the pulsatile rise of T is related to LH peaks and not to stages of sleep or prolactin peaks.