GI Hormones Lecture Notes

Practice flashcards covering the source, action, regulation, and clinical relevance of major gastrointestinal hormones as detailed in the lecture transcript.

Gastrin

A hormone produced by G cells in the antrum and duodenum that increases gastric acid secretion and gastric motility. It is stimulated by stomach distention, amino acids, and vagal stimulation via GRP, and inhibited by $pH < 1.5$.

Cholecystokinin (CCK)

Produced by I cells in the antrum and small intestine, its actions include increasing pancreatic enzyme secretion, gallbladder contraction, and sphincter of Oddi relaxation, while decreasing gastric emptying.

Secretin

A hormone from S cells in the duodenum that increases pancreatic $HCO_3^-$ secretion and bile secretion while decreasing gastric acid secretion. Its primary role is to neutralize gastric acid in the duodenum to allow pancreatic enzymes to function.

Somatostatin

Released by D cells, it acts to inhibit gastric acid and pepsinogen secretion, pancreatic and small intestine fluid secretion, gallbladder contraction, and the release of insulin and glucagon.

Octreotide

An analog of somatostatin used to treat acromegaly, carcinoid syndrome, VIPoma, and variceal bleeding; side effects include gallstones due to gallbladder stasis.

Glucose-dependent insulinotropic peptide (GIP)

Also known as gastric inhibitory peptide, it is released by K cells in the duodenum and jejunum. It decreases gastric $H^+$ secretion and increases insulin release in response to an oral glucose load.

Incretin effect of GIP

The phenomenon where an oral glucose load increases insulin levels significantly more than an equivalent intravenous (IV) glucose load due to the secretion of GIP.

Vasoactive intestinal polypeptide (VIP)

Produced in parasympathetic ganglia, it increases intestinal water and electrolyte secretion as well as relaxation of intestinal smooth muscle and sphincters; it is inhibited by adrenergic input.

WDHA Syndrome

A syndrome associated with VIPoma characterized by Watery Diarrhea, Hypokalemia, and Achlorhydria.

Ghrelin

A hormone produced by the stomach that increases appetite. Levels increase during the fasting state and in Prader-Willi syndrome, and decrease after food intake or gastric bypass surgery.