Secretin is a 27-aa peptide hormone secreted as a 121-aa inactive precursor by the intestinal glands of the duodenum. Secretin regulates homeostasis throughout the body and influences the environment of the duodenum by regulating secretions in the stomach and pancreas. Secretin stimulates the production of manceratic juices and bile rich in NaHCO3. It also stops the production of HCl by the stomach. Secretin belongs to the glucagon family sharing sequence homology with glucagon, VIP and GIP.