Ghrelin, the only circulating hormone that potently stimulates growth hormone secretion apart from GHRH, is produced mainly by which tissue and acts through which mechanism?
- A Gastric fundus oxyntic mucosa; activation of the GHS-R growth hormone secretagogue receptor on somatotrophs and hypothalamic neurons ✓
- B Pancreatic alpha cells; activation of the glucagon receptor on somatotrophs
- C Duodenal enterochromaffin cells; inhibition of somatostatin release from pancreatic delta cells
- D Adipose tissue; activation of leptin receptors in the arcuate nucleus
Correct answer: A. Gastric fundus oxyntic mucosa; activation of the GHS-R growth hormone secretagogue receptor on somatotrophs and hypothalamic neurons
Explanation
Ghrelin is acylated in gastric oxyntic mucosa and binds the growth hormone secretagogue receptor (GHS-R) on pituitary somatotrophs and hypothalamic GHRH neurons, amplifying GH pulses and also stimulating appetite via NPY/AgRP neurons. It rises before meals and during fasting. Leptin comes from adipose tissue and suppresses appetite, so option D mixes two opposite signals, and ghrelin has no relation to glucagon or delta cell pathways.
Reference: Ganong's Review of Medical Physiology, 26th ed.
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