Topic overview

Start with the big picture

GI hormones travel through the bloodstream to influence distant targets. The snapshot highlights gastrin, which increases acid secretion and motility; CCK, which triggers bile release and slows gastric emptying; secretin, which promotes bicarbonate secretion and inhibits acid; and GIP, which stimulates insulin release in response to oral glucose. Paracrines act locally: somatostatin inhibits many GI hormones and secretions, while histamine amplifies acid secretion through H₂ receptors. Neurocrines released by enteric neurons include VIP, which relaxes smooth muscle and stimulates bicarbonate secretion; GRP, which triggers gastrin release; and NO, which relaxes smooth muscle. Clinical links include VIPoma, Zollinger–Ellison syndrome, and therapeutic use of somatostatin analogs such as octreotide.