Ghrelin, an acetylated peptide composed of 28 amino-acids, is an endogenous ligand for the growth hormone secretagogues receptor, GHS-R. Ghrelin is mainly produced by the X/A cells of the oxyntic glands in the stomach and, to a much lesser extent, in hypothalamus, pituitary, adrenal gland, intestine, gonads, heart, T lymphocytes, and monocytes. Ghrelin increases growth hormone secretion independently on and synergistically with somatoliberin. It is the only peripheral hormone that increases appetite and food intake by stimulating hypothalamic neurons that secrete key orexinogens, neuropeptide Y and AgRP, and by inhibiting anorexigenic α-MSH neurons. Serum level of ghrelin increases during fasting and becomes suppressed by refeeding and in obesity. Ghrelin increases secretory activity and motility of stomach and ileum, induces proliferation of some cell lines and shows gastro- and cardiopro- tective properties.