Secretin may be a hormone that regulates water homeostasis throughout the body and influences the environment of the duodenum by regulating secretions within the stomach, pancreas, and liver. It's a peptide hormone produced within the S cells of the duodenum, which are located within the intestinal glands. In humans, the SCT gene encodes the secretin peptide.
Secretin is also responsible for stimulating the gall bladder, inhibiting acid secretion in stomach and in stimulating bicarbonate secretion by pancreas.