The nocturnal increase of plasma testosterone (T) in adult men has been well established. Luteinizing hormone (LH) does not show a similar increase throughout the night, whereas prolactin (PRL) does, suggesting the possibility of other hormone influence on T secretion. To investigate this possibility, 8 young adult men were studied for 4 consecutive nights in the sleep laboratory (2 nights adaptation, 2 nights blood sampling), by blood samples taken every 30 min during the 8-h sleep period, for measurement of LH, follicle stimulating hormone (FSH), PRL, and T. LH and FSH were secreted episodically, with little or no change in baseline levels during the night. PRL and T also were secreted episodically, but their baseline levels increased as the night progressed. Both LH and PRL had maximum within-subject correlations (averages equal +0.35 and +0.48 respectively) with T when they led T by 60 min. Within-subject correlations done on first differences (to remove the effect of slow trends) were near zero. LH and PRL had larger correlations with T than did FSH, for both calculations. These data suggest that both LH and PRL levels precede T levels by about 60 min. PRL thus may participate in the regulation of nocturnal T secretion in adult men.

Renal conservation of electrolytes and water occurs normally during sleep. Antidiuretic hormone (ADH), aldosterone (ALDO), and prolactin (PRL) are hormones that may have interactive effects on kidney function. The availability of a radioimmunoassay for ADH as well as for ALDO and PRL permitted the study of the simultaneous secretion patterns of these three hormones during all-night sleep in eight normal young adult men, by blood sampling every 20 min from 2300 to 0700 on two consecutive night. ADH, ALDO, and PRL all appeared to be secreted episodically. The pulsatile release of ADH was random, and average plasma ADH levels were unchanged during the night. ALDO and PRL, on the other hand, had an approximately 90-min secretion rhythm, and average plasma concentrations of both hormones consistently increased during the hours of sleep. Average plasma sodium concentration was constant throughout the night. The nocturnal increase in plasma ALDO may be responsible for the normal reduction of urine sodium excretion during the night. The concomitant increase in plasma PRL might synergize with ALDO in influencing the renal retention of sodium, but PRL alone has little apparent effect on human kidney function. REM sleep-related decreases in urine flow have been noted both in humans and in monkeys, but ADH secretion was not REM related in out subjects. Autonomic activation during REM is one possible explanation for decreased urine flow during this stage of sleep.

The patterns of LH, FSH and GH release during all-night sleep were studied in 16 normal young adult men, sampled on two consecutive nights. The release of both gonadotropins occurred in random, unrelated peaks that showed no consistency between subjects or from night to night in the same subject. No circadian or ultiadian rhythm was discernible for either LH or FSH. When analyzed by sleep stages, LH levels showed a modest but significant increase (14%) during REM sleep compared to the other stages of sleep. FSH levels, on the other hand, showed no clear relationship to sleep stages. Growth hormone did show the usual marked increase coincident with the onset of slow wave sleep.