Endocrine and metabolic activities of a recently isolated peptide hormone ghrelin, an endogenous ligand of the growth hormone secretagogue receptor.

Ghrelin is a member of the group of growth hormone secretagogues (GHSs). It is a peptide hormone, recently isolated from stomach as an endogenous ligand for the growth hormone secretagogue receptor (GHS-R). Ghrelin is mostly produced by the stomach, although its production has been proved in various tissues. It is a potent releaser of growth hormone (GH) from anterior pituitary cells, but it also stimulates the release of other hypophyseal hormones. Ghrelin stimulates food intake and induces metabolic changes leading to an increase in body weight and body fat mass. This effect seems to be independent of GH action and needs an intact NPY/AGRP (neuropeptide Y/agouti-related protein) system. Plasma ghrelin levels are decreased in obesity, elevated in cachexia and show a diurnal rhythm. Its preprandial elevation suggests, that it might be a signal for meal initiation. Ghrelin further stimulates the release of gastric acid and gastric motility and affects pancreatic functions. It has vasodilatatory, cardioprotective and antiproliferative effects. This article is focused on ghrelin's endocrine and metabolic functions.