Hormones Tissues of Origin Dietary Functions Secretory Stimuli
Cholecystokinin Enteroendocrine I cells and enteric nerves
  • Inhibits proximal gastric motility while increasing antral and pyloric contractions
  • Regulates meal-stimulated pancreatic enzyme secretion and gallbladder contraction
  • Trophic effects on pancreatic acini in rats
  • Postprandial satiety
  • Oral nutrient ingestion, especially lipids and proteins
  • Several intestine-derived hormones, including GRP
  • Activation of β-adrenergic receptors
Gastrin Enteroendocrine G cells of the stomach and duodenal bulb
  • Amidated gastrins are trophic to the oxyntic mucosa of the stomach
  • Progastrin and glycine-extended gastrin induce colonic epithelial proliferation
  • Luminal contents, especially partially digested aromatic amino acids, small peptides, calcium, coffee, and ethanol
  • Humoral and neural influences, including the vagus nerve, β-adrenergic and GABA neurons, and GRP
Gastric Inhibitory Polypeptide Neuroendocrine K cells in the duodenum and proximal jejunum
  • Inhibits gastric acid secretion and GI motility
  • Increases insulin release and regulates glucose and lipid metabolism
  • Oral nutrient ingestion, especially long-chain fatty acids
Motilin Enteroendocrine M cells located in the duodenum and proximal jejunum
  • Induces phase III contractions in the stomach
  • Stimulates gastric and pancreatic enzyme secretion
  • Induces contraction of the gallbladder, sphincter of Oddi, and LES
  • Duodenal alkalinization, sham feeding, gastric distention; opioid agonists promote secretion
  • Unlike most GI hormones, motilin is suppressed in the presence of duodenal nutrients
Secretin Enteroendocrine S cells located in the duodenum and proximal jejunum
  • Principal hormonal stimulant of pancreatic and biliary bicarbonate and water excretion
  • Regulates pancreatic enzyme secretion
  • Stimulates gastric secretion of pepsinogen
  • Inhibits LES tone, postprandial gastric emptying, gastrin release, and gastric acid secretion
  • Gastric acid, bile salts, and luminal nutrients, especially fatty acids, peptides, and ethanol
  • Somatostatin inhibits secretion
Somatostatin Enteroendocrine D cells and pancreatic delta cells
  • Inhibits secretion of islet hormones, including insulin, glucagon, and PP
  • Inhibits secretion of gut peptides, including gastrin, secretin,VIP, CCK, GLP1 and GLP2
  • Inhibits pancreatic exocrine secretion Acts in a paracrine manner on G cells, enterochromaffin-like cells, and parietal cells to inhibit gastric acid secretion
  • Reduces splanchnic blood flow, intestinal motility, and carbohydrate absorption while increasing water and electrolyte absorption
  • Luminal nutrients
  • Gastrin, CCK, bombesin, GLP1, and GIP
  • Neural influences, including PACAP,VIP, and β-adrenergic agonists stimulate while ACh inhibits secretion
Vasoactive Intestinal Polypeptide Enteric nervous system
  • Induces relaxation of vascular and nonvascular smooth muscle
  • Mediates relaxation of the LES, sphincter of Oddi, and anal sphincter
  • Regulates relaxation-associated gut contraction and may be involved with reflex vasodilation in the small intestine
  • Inhibits gastric acid secretion
  • Stimulates biliary water, bicarbonate, pancreatic enzyme, and intestinal chloride secretion
  • Mechanical stimulation
  • Activation of the CNS and PNS