Ghrelin is the 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. Obestatin may be the ligand for GPR39. May have an appetite-reducing effect resulting in decreased food intake. May reduce gastric emptying activity and jejunal motility (By similarity). Mainly expressed in the gastrointestinal tract with higher levels in the stomach, medium levels in the duodenum, jejunum, ileum and colon. Low expression in the testis and brain. Not detected in the salivary gland, pancreas, liver and lung. Levels of n-octanoylated and n-decanoylated ghrelin drop by one third and 3-fold, respectively, between postnatal weeks 3 and 4 due to change of diet during weaning. O-octanoylated by GOAT/MBOAT4 (PubMed:18443287). O-octanoylation or O-decanoylation is essential for ghrelin activity (By similarity). The O-decanoylated form ghrelin-C10 differs in the length of the carbon backbone of the carboxylic acid bound to Ser-26 (PubMed:15746259). Amidation of Leu-98 is essential for obestatin activity. Ghrelin, O-octanoylated form. Belongs to the motilin family. Gut feelings - Issue 66 of January 2006