Sexually dimorphic effects of GHRH on sleep-endocrine activity in patients with depression and normal controls - part I: the sleep eeg.

In patients with depression, enhanced secretion of ACTH and cortisol, a reduction in slow wave sleep (SWS) and a blunted nocturnal growth hormone (GH) surge have been described and attributed, at least partly, to an elevation of corticotropin-releasing hormone (CRH), hence a shift in the ratio between growth hormone-releasing hormone (GHRH) and CRH. We investigated the effects of pulsatile administration of GHRH (4x50 microgram, at hourly intervals between 2200 and 0100 h) on the sleep EEG (2300-0700 h) in patients with depression (16 females, 19 males, age range 19-76 years) and matched controls (20 females, 20 males). In patients compared with controls, NREM sleep and in particular stage 2 sleep was greatly decreased at baseline. GHRH treatment enhanced NREM sleep, and in particular stage 2 sleep in men, regardless of diagnosis, while decreasing it in women (F=6.0 and 7.1, p<0.05). In controls, aging was associated with a decrease in NREM sleep, including both SWS and stage 2 sleep (r= -0.45 r= -0.39, p<0.05), while in patients only SWS declined with age (r= -0.49, p<0.05). The significant decrease in NREM sleep including stage 2 sleep in patients with depression and elderly control subjects is compatible with the suggested role of sleep continuity and stage 2 sleep in cognitive functioning. GHRH promoted NREM sleep, stage 2 sleep and sleep continuity and might prove beneficial for improvement of cognitive function, at least in men. These data support the hypothesis that female gender, aging and depression are associated with a shift in the GHRH/CRH ratio towards CRH.