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GHRH impairs sleep in normal females
GHRH stimulates GH and slow wave sleep (SWS) and inhibits cortisol in young normal male subjects. In females of a wide age range GHRH, however, impaired sleep, ACTH and cortisol when given during consecutive nights. We examined sleep EEG and nocturnal hormone concentrations by blood sampling of GH, ACTH, cortisol, in 7 healthy young females subjects (age: mean±SD 26.3±3.3 years) after pulsatile iv administration of 4×25µg GHRH (A, GHRH 25µg), 4×50µg GHRH (B, GHRH 50µg) or placebo (C) according to randomized schedule. To exclude effects of gonadal steroids each the sessions were performed at day 4–6 of the menstrual cycle during a 3 months period. After GHRH 50µg sleep stage 4 decreased significantly during the total night compared to placebo whereas GHRH 25µg showed no significant effect (p<0,01). Furthermore, in the first half of the night a significant decrease of REM sleep was observed after GHRH 25µg (p<0,05) and GHRH 50µg (p<0,07). The hormone concentrations of GH were enhanced in the total night after GHRH 25µg and GHRH 50µg (p<0.05) as well as in the first half of the night (p<0.05). Cortisol and ACTH levels did not differ between groups. These data are in agreement with our previous study showing that GHRH is capable to impair sleep in healthy females. In the present study we could not observe changes in cortisol and ACTH levels which might be due to a different age range and administration setting of GHRH.