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Ghrelin

Gastric fundus-derived peptide hormone (the only known peripheral orexigen) that rises premeally and falls postmeally, stimulating hunger via hypothalamic NPY/AgRP neurons.

Ghrelin requires acylation by ghrelin O-acyltransferase (GOAT) to bind its receptor (GHSR). Acyl-ghrelin levels are paradoxically lower in obesity and higher in anorexia nervosa, indicating it is not a simple feedback hormone but an adaptive regulator. Bariatric surgery (especially sleeve gastrectomy) reduces ghrelin, contributing to its appetite effects. Prader-Willi syndrome has elevated ghrelin and intractable hyperphagia.

How each textbook covers it

Advanced Nutrition and Human Metabolism, 8th ed. (Gropper) — Glossary
Peptide hormone produced primarily by gastric oxyntic cells. Rises before meals to stimulate appetite via the hypothalamic arcuate nucleus and falls after eating. Acts on the growth hormone secretagogue receptor.
Modern Nutrition in Health and Disease, 12th ed. — Ch 43: Appetite Regulation
Ghrelin requires acylation by ghrelin O-acyltransferase (GOAT) to bind its receptor (GHSR). Acyl-ghrelin levels are paradoxically lower in obesity and higher in anorexia nervosa, indicating it is not a simple feedback hormone but an adaptive regulator. Bariatric surgery (especially sleeve gastrectomy) reduces ghrelin, contributing to its appetite effects. Prader-Willi syndrome has elevated ghrelin and intractable hyperphagia.

Related terms

Appetite regulation, Arcuate nucleus, GLP-1, Leptin, Obesity, Orexigenic