Which hormone most likely provoked the current epigastric pain after a fatty meal by stimulating gallbladder contraction?

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

Answer: (B)

Cholecystokinin is released from intestinal I cells in response to fats in the duodenum. It stimulates the gallbladder to contract and also relaxes the sphincter of Oddi, enabling bile to flow into the duodenum to emulsify fats. This mechanism explains why a fatty meal often prompts gallbladder contraction and can provoke epigastric pain if the gallbladder is irritated. Motilin mainly regulates interdigestive motility, not meal-induced gallbladder contraction; gastrin mainly increases gastric acid secretion; secretin promotes pancreatic bicarbonate secretion and slows gastric emptying. Hence the hormone most likely responsible for the gallbladder contraction after a fatty meal is cholecystokinin.