On the gender differences in sleep-endocrine regulation in young normal humans.

Sleep-endocrine regulation in humans involves high activity of the somatotropic axis at the beginning of the night and an increase in the hypothalamic-pituitary-adrenocortical (HPA) system during the night. Gender differences were examined with regard to sleep-endocrine regulation in young healthy controls (10 men, 9 women). The sleep EEG was recorded (23:00-07:00 h) and plasma samples were collected and analyzed for GH, cortisol and ACTH at 20-min intervals. Cortisol secretion was significantly higher in females during the first half of the night (F = 9.9, p < 0.05), while ACTH was not different. In women, sleep-EEG analysis showed less slow wave sleep (SWS) during the second half of the night (F = 4.5, p < 0.05) and a significantly greater decrease in SWS and delta activity from the first to the second half of the night (F = 3.7 and 7.4, respectively, p < 0.05). Sigma activity increased during the night in women only (F = 3.7, p < 0.05). Our data are compatible with the hypothesis that in women compared to men activity of hypothalamic CRH neurons and central CRH release is greater, but is not reflected by greater HPA activity.