The incretin concept today.

1. The insulinogenic factor of the gastrointestinal mucosa named "incretin" is only one part of the complex enteroinsular axis. --2. Of the chemically defined gastrointestinal hormones GIP is the strongest incretin candidate. --3. Because of the dual function of GIP as gastrone and insulinotropic substance several safeguards against GIP-mediated insulin hypoglycaemia exist. --4. No pathological condition has yet been found which is causally related to hyper- or hyposecretion of GIP. However, an exaggerated GIP response (usually secondary to the disease) may participate in the pathogenesis of hyperinsulinaemia of patients with obesity and duodenal ulcer. --5. The injection of GIP antibodies only partially abolishes the incretin effect. Therefore, GIP, although important, is not the only incretin.