Ghrelin and growth hormone secretagogues (GHS): modulation of growth hormone secretion and therapeutic applications

Growth hormone-releasing hormone (GHRH) and somatostatin modulate growth hormone (GH) secretion. A third mechanism was discovered in the last decade, involving the action of growth hormone secretagogues (GHS). Ghrelin, the endogenous ligand of the GHS-receptor, is an acylated peptide mainly produced by the stomach, but also synthesized in the hypothalamus. This compound increases both GH release and food intake. Endogenous ghrelin might amplify the basic pattern of GH secretion, optimizing somatotroph responsiveness to GHRH, activating multiple interdependent intracellular pathways. However, its main site of action is the hypothalamus. In the current paper it is reviewed the available data on the discovery of this peptide, the mechanisms of action and possible physiological roles of the GHS and ghrelin on GH secretion, and finally, the possible therapeutic applications of these compounds.