Which among the following is the function of ghrelin?
**Core Concept**
Ghrelin is a peptide hormone produced in the gastrointestinal tract, specifically in the stomach. It plays a crucial role in regulating appetite, energy balance, and metabolism. Ghrelin stimulates the release of growth hormone from the anterior pituitary gland, hence its name.
**Why the Correct Answer is Right**
Ghrelin acts on the arcuate nucleus of the hypothalamus, stimulating the release of neuropeptide Y (NPY) and agouti-related peptide (AgRP), which in turn increase appetite and food intake. Ghrelin also stimulates the release of growth hormone from the anterior pituitary gland, leading to increased glucose production and lipolysis. The ghrelin receptor, GHSR1a, is expressed in various tissues, including the hypothalamus, pituitary gland, and adipose tissue.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect. Ghrelin does not primarily function as a neurotransmitter in the central nervous system.
**Option B:** Incorrect. While ghrelin does stimulate appetite, its primary function is not to increase energy expenditure.
**Option C:** Incorrect. Ghrelin does not play a significant role in regulating blood pressure.
**Clinical Pearl / High-Yield Fact**
Ghrelin levels are typically highest in the morning and decrease throughout the day. Fasting or caloric restriction increases ghrelin levels, stimulating appetite and food intake.
**Correct Answer: C. Stimulation of appetite and growth hormone release.**