| Hormone | Site | Actions | Stimuli |
|---|
Primarily increases acid ($H^+$). Elevated in Zollinger-Ellison syndrome (Gastrinoma). Phenylalanine and Tryptophan are potent stimulators.
The "Stop" hormone. Inhibits Insulin, Glucagon, Gastrin. Octreotide is an analog used for variceal bleeding, acromegaly, and carcinoid.
Causes gallbladder contraction and pancreatic enzyme secretion. Causes pain in cholecystitis after fatty meals.
Neutralizes acid. Stimulates Pancreas to release Bicarbonate ($HCO_3^-$). Triggered by acid in duodenum.
Incretin Effect: Oral glucose stimulates more insulin than IV glucose due to GIP/GLP-1 release.
Produces Migrating Motor Complexes (MMCs) (growling) during fasting. Erythromycin is an agonist (treats gastroparesis).
"Hunger" hormone. Increased in fasting and Prader-Willi syndrome.
Increases water/electrolyte secretion. VIPoma causes WDHA syndrome (Watery Diarrhea, Hypokalemia, Achlorhydria).
Located in the Antrum of the stomach and Duodenum. Think "G" for Gastrin.
Found in Pancreatic Islets ($\delta$ cells) and GI Mucosa. Think "D" for Delta or "Decrease" (inhibition).
Located in Duodenum & Jejunum. Mnemonic: Increases gallbladder contraction and pancreatic enzymes.
Located in the Duodenum. S cells sense stomach acid arriving and release Secretin to call for Bicarb.
Located in Duodenum & Jejunum. Mnemonic: K cells for "Kandy" (Glucose), because GIP is released in response to oral glucose.
Located in Duodenum & Jejunum.
⚠️ Note: Do not confuse these with the "Microfold M cells" of Peyer's patches (immune sampling). These M cells solely regulate motility.
Located in the Fundus of the stomach. (Contrast with G cells in the Antrum).
VIP is a neurocrine, not a traditional hormone. It is released by parasympathetic ganglia in sphincters, gallbladder, and small intestine.