True about Secretin includes all of the following EXCEPT
**Core Concept**
Secretin is a hormone released by the duodenum in response to acidification, which stimulates pancreatic bicarbonate secretion and inhibits gastric acid secretion. It plays a crucial role in regulating the pH of the small intestine and facilitating nutrient absorption.
**Why the Correct Answer is Right**
Secretin acts through the activation of G-protein coupled receptors, specifically the secretin receptor (SCTR), which is expressed on the surface of pancreatic acinar cells and other target cells. The binding of secretin to its receptor triggers a cascade of intracellular signaling events that ultimately lead to the secretion of bicarbonate-rich fluid from the pancreas and inhibition of gastric acid secretion. This hormone also has trophic effects on the pancreas, promoting the growth and differentiation of pancreatic tissue.
**Why Each Wrong Option is Incorrect**
**Option A:** Secretin is known to stimulate pancreatic bicarbonate secretion, which is correct, so this option is not the answer.
**Option B:** Secretin inhibits gastric acid secretion, which is also correct, so this option is not the answer.
**Option C:** Secretin is released by the pancreas, not the duodenum, which is incorrect.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that secretin's effects are mediated through its interaction with the secretin receptor, and its release is triggered by the presence of acidic chyme in the duodenum. This hormone plays a vital role in maintaining the delicate balance of pH in the small intestine.
**Correct Answer: C. Secretin is released by the pancreas, not the duodenum, which is incorrect.