GIP is produced in the K cells of the small intestine. It binds to a specific GIP receptor, which is expressed in various tissues, including pancreatic beta cells, pancreatic alpha cells, subcutaneous and visceral adipose tissue, bone, and heart. In the postprandial state, GIP is co-secreted with GLP-1, and they appear to interact in an additive fashion to potentiate glucose-induced insulin secretion. However, GIP exhibits different effects than GLP-1 on glucagon secretion. In euglycemic or hypoglycemic states, GIP enhances glucagon activity.