Not true about ghrelin is
**Core Concept**
Ghrelin is a peptide hormone produced by the gastrointestinal tract, specifically by the stomach and small intestine. It plays a crucial role in regulating appetite, energy balance, and glucose metabolism. As a neuropeptide, ghrelin acts on the central nervous system to stimulate food intake and increase adiposity.
**Why the Correct Answer is Right**
Ghrelin acts on the growth hormone secretagogue receptor 1a (GHSR1a) in the hypothalamus, stimulating the release of growth hormone and increasing appetite. Ghrelin also has a role in modulating glucose metabolism by inhibiting insulin secretion and promoting glucagon release. This hormone is often referred to as the "hunger hormone" due to its orexigenic effects.
**Why Each Wrong Option is Incorrect**
**Option A:** Ghrelin is primarily produced by the pancreas. This is incorrect because ghrelin is primarily produced by the stomach and small intestine, not the pancreas.
**Option B:** Ghrelin has no role in regulating appetite. This is incorrect because ghrelin is known to stimulate appetite and increase food intake.
**Option C:** Ghrelin is a derivative of gastrin. This is incorrect because ghrelin is a distinct peptide hormone with its own receptor and mechanism of action, separate from gastrin.
**Clinical Pearl / High-Yield Fact**
Ghrelin levels typically decrease after eating and increase before meals, which is why it is often referred to as the "hunger hormone." This hormone plays a crucial role in energy balance and glucose metabolism, making it a key target for the development of anti-obesity therapies.
**Correct Answer:** B. Ghrelin has no role in regulating appetite.