The three main mammalian gastrointestinal hormones are secretin, gastrin and cholecystokinin (CCK). There are several other hormones all peptides. The physiology of only three major hormones is listed in Table.
Table: Mammallan gastrointestinal hormones; - denotes inhibition; + stimulation; +++hormone more important than other two
Gastrin secretion is responsible for control of HCI volume; the presence of HCI in turn inhibits further gastrin secretion.