EFFECTS OF PULSATILE CORTISOL INFUSION ON SLEEP-EEG AND NOCTURNAL GROWTH-HORMONE RELEASE IN HEALTHY-MEN

This study investigates the short-term effects of pulsatile cortisol a dministrations upon sleep electroencephalogram (EEG) and spontaneous r elease of growth hormone (GH) in humans. Ten young healthy male volunt eers received intravenous injections of either placebo or cortisol eve ry 60 min between 17.00 hours and 06.00 hours (1 mg kg-1 BW with a loa ding dose of 20% starting at 17.00 hours, followed by a dose of 6% eve ry hour until 06.00 hours). The amount of rapid eye-movement (REM) sle ep was significantly reduced (placebo: 19.9 +/- 1.8; cortisol: 12.2 +/ - 1.5%; P < 0.05), whereas the time spent in slow-wave sleep (SWS) was significantly increased (placebo: 9.4 +/- 1.6; cortisol: 13.9 +/- 1.9 %; P < 0.05). The SWS-promoting effect was most prominent during the f irst hours of sleep, but tended to persist also during the second half of the night. The pulsatile cortisol administration augmented the tot al amount of plasma GH concentrations (mean area under the time course curve, AUC, placebo: 3.2 +/- 0.5; cortisol: 4.4 +/- 0.6 [ng x 1000 x ml min-1]; P < 0.05) due to an increase of GH release before sleep ons et, and during the second half of the night, while the GH surge at sle ep onset remained unchanged. Our data are in accordance with the hypot heses that cortisol-induced changes of both sleep-EEG and GH secretion involve a common mechanism that includes activation of the hypothalam ic-somatotrophic (growth hormone releasing hormone-growth hormone) sys tem.