This gene encodes a G-protein coupled receptor for gastric inhibitory polypeptide (GIP), which 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 in the presence of elevated glucose. Mice lacking this gene exhibit higher blood glucose levels with impaired initial insulin response after oral glucose load. Defect in this gene thus may contribute to the pathogenesis of diabetes. [provided by RefSeq, Oct 2011]