What is Ghrelin?
A naturally occurring 28-amino acid gut-brain growth hormone releasing peptide (GHRP) that is expressed mainly in the stomach and possibly in the hypothalamus. Fasting and hypoglycemia increase ghrelin levels and circulating ghrelin levels are decreased in chronic obesity, following acute caloric intake and in states of positive energy balance. Acute administration of ghrelin to humans induces a feeling of hunger. Ghrelin binds to ghrelin-receptors in the anterior pituitary and possibly in the mediobasal and mediolateral hypothalamus to stimulate growth hormone release and to regulate energy homeostasis. Serum levels of ghrelin are measurably higher in patients who have lost weight through dietary measures.