Ghrelin, the "hunger hormone", also known as lenomorelin, is a peptide hormone produced by ghrelinergic cells in the gastrointestinal tract. Ghrelin functions as a neuropeptide in the central nervous system. Besides regulating appetite, it also plays a significant role in regulating energy homeostasis. Ghrelin cells are found mainly in the stomachand duodenum, but also in the jejunum, lungs, pancreatic islets, gonads, adrenal coex, placenta, and kidney. It has recently been shown that ghrelin is produced locally in the brain Ghrelin has been linked to inducing appetite and feeding behaviors. Circulating ghrelin levels are the highest right before a meal and the lowest right after.Injections of ghrelin in both humans and rats have been shown to increase food intake in a dose-dependent manner. So the more ghrelin that is injected the more food that is consumed. However, ghrelin does not increase meal size, only meal number.Ghrelin injections also increase an animal's motivation to seek out food, behaviors including increased sniffing, foraging for food, and hoarding food. Body weight is regulated through energy balance, the amount of energy taken in versus the amount of energy expended over an extended period of time. Studies have shown that ghrelin levels are negatively correlated with weight. This data suggests that ghrelin functions as an adipositysignal, a messenger between the body's energy stores and the brain Ref guyton and hall hall textbook of medical physiology 12th edition pg 554