Which hormone primarily slows gastric emptying and stimulates pancreatic enzyme secretion and gallbladder contraction?

• A. Secretin
• B. Cholecystokinin
• C. Gastrin
• D. Motilin

Answer: (B)

Cholecystokinin (CCK) is the hormone that fits these actions. It’s released by I cells in the duodenum and proximal jejunum when fatty or protein-rich chyme enters the small intestine. Its main job is to coordinate digestion: it slows gastric emptying by reducing stomach motility so the chyme has time to be broken down, while simultaneously signaling the pancreas to release enzyme-rich juice needed for digestion. CCK also triggers the gallbladder to contract, pushing bile into the duodenum, and it relaxes the sphincter of Oddi to let bile and pancreatic secretions enter the intestine. By contrast, secretin mainly stimulates bicarbonate secretion to neutralize acid, gastrin mainly increases gastric acid production, and motilin drives fasting motility patterns, not the combination described. Hence, CCK is the hormone that best matches all three effects.