Gastric Inhibitory Polypeptide Receptor is a member of the G protein-coupled receptor (GPCR, or GPR) family (subfamily Gastric inhibitory polypeptide). Members of this family contain 7 transmembrane domains and transduce extracellular signals through heterotrimeric G proteins. Gastric inhibitory polypeptide receptor is a receptor for gastric inhibitory polypeptide (GIP), this is a 42-amino acid polypeptide synthesized by K cells of the duodenum and small intestine. It was originally identified as an activity in gut extracts that inhibited gastric acid secretion and gastrin release, but subsequently was demonstrated to stimulate insulin release potently in the presence of elevated glucose. The insulinotropic effect on pancreatic islet beta-cells was then recognized to be the principal physiologic action of GIP. Together with glucagon-like peptide-1, GIP is largely responsible for the secretion of insulin after eating. It is involved in several other facets of the anabolic response. GIPR expression has been reported in human bone, fetal adrenal, and pancreas. Little expression has been identified in normal adult adrenal, but overexpression of GIPR has been observed in the adrenal in food- dependent Cushing's syndrome. GIPR expression has been identified in rat brain, heart, pancreas, and small intestine. ESTs have been isolated from colon libraries.