Introduction

Although Claude Bernard in the 1850s suggested the presence of blood borne messengers capable of regulating metabolic functions, it was not until the beginning of the Twentieth Century with the work of Bayliss and Starling that the existence of circulating regulatory factors or hormones was finally established. The enteric endocrine system played a central role in the validation of hormonal regulatory processes with the first hormone identified being secretin, released from the upper intestine to stimulate pancreatic secretion. However, unlike the majority of the endocrine glands (thyroid, adrenal, and so on), the endocrine cells within the gastrointestinal tract are not grouped together into distinct organs or substructures. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.