Ghrelin is an endogenous ligand for the growth hormone secretagogue receptor. it is synthesized as ghrelin/obestatin propeptide (preproghrelin) principally in the stomach. Ghrelin is present in the peripheral circulation under two forms: acylated and unacylated. The acylated-ghrelin consists of 28 amino acids, with an n-octanoylation of the serine-3 residue. It stimulates food intake and transduces signals to hypothalamic regulatory nuclei that control energy homeostasis. It is interesting that ghrelin functions as an appetite activater, while its “brother“ obestatin is an appetite suppressor.