Gastric inhibitory peptide (GIP) is a gastrointestinal hormone secreted by the duodenum. Formerly, it was believed to neutralize stomach acid to protect the small intestine from acid damage as well as reduce the rate at which food is transferred through the stomach. However, it was discovered that these effects are only achieved with GIP levels higher than the physiological level. These results naturally occur in the body through another gastrointestinal hormone of the same family, secretin. It is now believed that the function of GIP is to induce insulin secretion after glucose is detected in the small intestine. After this discovery, it was given a new name, glucose-dependent insulinotropic peptide, but still uses GIP as an acronym.