The endocrinology of the gastrointestinal tract is complex and incompletely understood. The first hormone described, secretin, was isolated from the gastrointestinal tract in 1902. Further advances in gastrointestinal endocrinology, however, were limited until recently, when reliable techniques for isolating regulatory peptides at extremely low concentrations became available.
A variety of gastrointestinal pathologies are associated with significant alterations in circulating concentrations of gut peptides and it is thought that, under these circumstances, they play a role in the adaptation of the gut: for example, in response to loss of absorptive or secretory surface by altering secretion and motility in unaffected regions.
