Gastric inhibitory polypeptide (GIP), is a member of the secretin family of hormones.GIP is derived from a 153-amino acid proprotein encoded by the GIP gene and circulates as a biologically active 42-amino acid peptide. It is synthesized by K cells, which are found in the mucosa of the duodenum and the jejunum of the gastrointestinal tract.Like all endocrine hormones, it is transported by blood. It is now believed that the function of GIP is to induce insulin secretion, which is primarily stimulated by hyperosmolarity of glucose in the duodenum. After this discovery, some researchers prefer the new name of glucose-dependent insulinotropic peptide, while retaining the acronym "GIP." The amount of insulin secreted is greater when glucose is administered orally than intravenously.