Ghrelin is a hormone which is principally released from the stomach and acts in the hypothalamus to signal hunger, stimulate appetite, reduce energy expenditure and increase fat storage. Levels are highest before mealtimes and it may also play a role in stimulating gastric motility and acid secretion in preparation for food.
In addition, ghrelin acts on the anterior pituitary to stimulate the release of growth hormone and on pancreatic islet cells to reduce insulin release.
Low levels are associated with: obesity (although it is thought that obese individuals have increased ghrelin receptor sensitivity); chronic gastritis; functional dyspepsia; IBS; and H. Pylori infection.
High levels are associated with: caloric restriction; anorexia nervosa; cachexia; IBD; Coeliac disease: and Prader-Willis Syndrome.