Gastrointestinal hormone upon their chemical structure. Ghrelin is a peptide hormone released from the stomach and liver and is often referred to as the "hunger hormone" since high levels of it are found in individuals that are fasting. Ghrelin agonistic treatments can be used to treat illnesses such as anorexia and loss of appetites in cancer patients. Ghrelin treatments for obesity are still under intense scrutiny and no conclusive evidence has been reached. This hormone stimulates growth hormone release. Amylin controls glucose homeostasis and gastric motility Glucose-dependent insulinotropic polypeptide possesses an acute influence on food intake through its effects on adipocytes Oxyntomodulin
Ghrelin increase fear learning. Ghrelin was found to be upregulated by stress even in the absence of adrenal hormones. Blocking the ghrelin receptor during stress abolished stress-related enhancement of fear memory without blunting other markers of stress. These results suggest that ghrelin is a novel branch of the stress response. Human studies are needed to translate the use of anti-ghrelin treatments to prevent stress-induced psychiatric disorders. Ghrelin, through its receptor increases the concentration of dopamine in the substantia nigra. Ghrelin has inhibitory effects on gonadotropin-releasing hormone (GnRH) secretion. It may cause decreased fertility. Gastric bypass surgery not only reduces the gut's