[Trp3, Arg5]-Ghrelin (1-5) is a Growth-Hormone Secretagogue (GHS) receptor agonist which stimulates growth hormone release . The full lenth 28 amino acid peptide Ghrelin is a peptide hormone that regulates appetite, energy balance, meal initiation and nutrient sensing. Ghrelin is produced in the stomach, but is also found in the blood, brain, and other tissues.. It influences bodily functions through associating with growth hormone secretagogue receptors (GHS-R) through its unique N-octanoyl group which is linked to its serine 3 residue covalently. It wider functions are in the regulation of insulin resistance, diabetes and obesity. On top of this Ghrelin is also found to be involved with glucose homeostasis, energy homeostasis, cardio-protective effects, bone metabolism and is a potential target for cancer. Therefore it can be used to develop therapies for a whole spectrum of diseases. This molecule is used as a research tool for studying cell biology and pharmacology.