Ligand for growth hormone secretagogue receptor type 1 (GHSR). Induces the release of growth hormone from the pituitary. Has an appetite-stimulating effect, induces adiposity and stimulates gastric acid secretion. Involved in growth regulation. High levels in stomach. Moderate levels in small intestine, pancreas and testis. Low levels in heart, lung and gall bladder. O-octanoylated by GOAT/MBOAT4 (By similarity). O-octanoylation or O-decanoylation is essential for activity. The O-decanoylated form ghrelin-27-C10 differs in the length of the carbon backbone of the carboxylic acid bound to Thr-27. 33% of frog ghrelin is O-decanoylated (PubMed:11546772). 80% of frog ghrelin has Asn-52 cleaved from its C-terminus giving rise to ghrelin-27. Ghrelin-28-C8, O-octanoylated form. Ghrelin-27-C10, O-decanoylated form. Ghrelin-28-C8, O-octanoylated form. Belongs to the motilin family.