A 24-year-old man undergoing an overnight fast shows a rise in circulating acylated peptide secreted by gastric fundus oxyntic cells just before his expected meal time. This hormone stimulates GH release by acting on which receptor at the pituitary and hypothalamus?
- A Growth hormone receptor (JAK2-STAT5)
- B GH secretagogue receptor (GHS-R1a) ✓
- C Somatostatin receptor subtype 2
- D Dopamine D2 receptor
Correct answer: B. GH secretagogue receptor (GHS-R1a)
Explanation
Ghrelin, produced mainly by X/B-like cells of the gastric fundus, rises preprandially and binds the growth hormone secretagogue receptor GHS-R1a on somatotrophs and on hypothalamic neurons, potentiating GH pulse amplitude. It also increases appetite via NPY/AgRP neurons. The GH receptor mediates IGF-1 generation after GH binds, not ghrelin signalling. Somatostatin receptors mediate inhibition, and D2 receptors relate to prolactin control.
Reference: Ganong's Review of Medical Physiology, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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