Ghrelin, an acylated peptide consisting of 28 amino acids, is the endogenous ligand of the growth hormone secretagogue receptor (GHS-R). It is synthesized predominantly in the stomach but has been also identified in a variety of other organs. Alike, a wide range of central and peripheral endocrine and non-endocrine actions has been described, e. g. being a releasing factor of growth hormone, prolactin and ACTH, a modulator of cell proliferation and apoptosis, a regulator of sleep-wake regulation, and a orexigenic hormone. Aims of this study are:

A) To determine the effect of exogenous ghrelin on sleep-EEG variables and hormones of the hypothalamic-pituitary-adrenocortical (HPA) axis, the gonadotropic axis and the hypothalamic-pituitary-gonadal axis in healthy subjects of both genders (age groups: 20-30, 35-45, 60-70 years).

B) To determine the effect of exogenous ghrelin on sleep-EEG variables and hormones of the HPA axis, the gonadotropic axis and the hypothalamic-pituitary-gonadal axis in patients with major depression (age range: 20-65 years).