«Ghrelin (pronounced /ˈɡrɛlɪn/), the "hunger hormone", also known as lenomorelin (INN), is a peptide hormone produced by ghrelinergic cell in the gastrointestinal tract that functions as a neuropeptide in the central nervous system. Besides regulating appetite, ghrelin also plays a significant role in regulating the distribution and rate of use of energy.
When the stomach is empty, ghrelin is secreted. When the stomach is stretched, secretion stops.a It acts on hypothalamic brain cell both to increase hunger, and to increase gastric acid secretion and gastrointestinal motility to prepare the body for food intake.
The receptor for ghrelin, the ghrelin/growth hormone secretagogue receptor (GH-R), is found on the same cell in the brain as the receptor for leptin, the satiety hormone that has opposite effects from ghrelin. Ghrelin also plays an important role in regulating reward perception in dopamine neurons that link the ventral tegmental area to the nucleus accumbens (a site that plays a role in processing sexual desire, reward, and reinforcement, and in developing addictions) through its colocalized receptors and interaction with dopamine and acetylcholine. Ghrelin is encoded by the GHRL gene and is presumably produced from the cleavage of the prepropeptide ghrelin/obestatin. Full-length preproghrelin is homologous to promotilin and both are members of the motilin family.
Unlike the case of many other endogenouspeptides, ghrelin is able to cross the blood-brain-barrier, giving exogenously-administered ghrelin unique clinical potential.» (wikipedia)