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Nocturnal ghrelin levels in normal controls – effects of gender
The neuropeptide ghrelin was recently identified as an endogenous ligand of the growth hormone (GH) secretagogue receptor. Besides GH-releasing hormone ghrelin is an endogenous stimulus of GH. We showed recently that ghrelin promotes slow wave sleep and the nocturnal release of cortisol and prolactin. It is thought that a reciprocal interaction of ghrelin and leptin exists in the regulation of the energy balance. We suggest that ghrelin acts as an interface of the hypothalamo-pituitary adrenocortical (HPA) and hypothalamo-pituitary somatotrophic systems. No data are available on the sleep related pattern of ghrelin secretion.
We examined simultaneously sleep EEG and the nocturnal secretion of ghrelin and GH in normal controls (females n=8, males n=8). With regard to gender differences and the course of ghrelin we found a significant interaction indicating an overnight increase in males and steady concentrations in females Stage 1 sleep in the second half of the night was lower in female subjects. Lower time spent in stage 1 sleep during the night was observed in subjects with high ghrelin AUC. In contrast to the pattern of the GH secretion no systematic association of the time of ghrelin peaks and sleep-wake-behaviour was detected.
A clear link between nocturnal GH and ghrelin secretion was not found. Our data point to different patterns of ghrelin secretion in women and men.