(1) Insulin

(2) Leptin

(3) Ghrelin

(4) PYY hormone

Ghrelin is the hormone that stimulates appetite, acting as the primary “hunger hormone” released by the stomach during fasting.

Question Breakdown

This question targets endocrine regulation of feeding behavior, a key concept in biochemistry and physiology for life sciences students, especially in topics like metabolic pathways and hormonal signaling for GATE exams.

Option Explanations

• Insulin: Produced by pancreatic beta cells, insulin lowers blood glucose by promoting uptake and storage; it suppresses appetite post-meal via hypothalamic signaling, not stimulates it.

• Leptin: Secreted by adipose tissue, leptin signals satiety to the hypothalamus by inhibiting orexigenic neurons, reducing food intake as fat stores increase.

• Ghrelin: Released from gastric fundus cells during fasting, ghrelin rises pre-meal to activate NPY/AgRP neurons in the arcuate nucleus, strongly stimulating hunger and food intake.

• PYY hormone: Postprandially secreted by intestinal L-cells, peptide YY (PYY) acts as an anorexigenic gut hormone, enhancing satiety and reducing appetite via Y2 receptors.

Introduction to Appetite Stimulating Hormone

The hormone which stimulates an appetite is ghrelin, driving hunger signals from stomach to brain during fasting. This contrasts with satiety hormones, crucial for metabolic balance in obesity research.

Ghrelin Mechanism

Ghrelin binds GHS-R1a receptors, activating hypothalamic orexigenic pathways (NPY/AgRP) while inhibiting POMC neurons, boosting meal initiation and size. Levels peak pre-meal, dropping postprandially.

Hormone Comparison

Ghrelin uniquely promotes feeding.

Relevance in Biochemistry

Targets for anti-obesity drugs (e.g., GLP-1 agonists counter ghrelin); aligns with enzymology of signaling cascades in graduate studies.