Growth hormone secretion is governed by dual hypothalamic control. Which pair correctly matches each hypothalamic hormone with its receptor-linked signalling pathway in the somatotroph?

• A GHRH via Gq and increased IP3; somatostatin via Gs and increased cAMP
• B GHRH via Gs and increased cAMP; somatostatin via Gi and decreased cAMP ✓
• C GHRH via Gi and decreased calcium; somatostatin via Gq and increased IP3
• D GHRH via tyrosine kinase and JAK-STAT; somatostatin via Gq and increased IP3

Explanation

GHRH binds a G protein coupled receptor linked to Gs, raising cAMP and activating protein kinase B, which promotes GH gene transcription and secretion. Somatostatin couples to Gi, lowering adenylyl cyclase activity and blunting cAMP generation, thereby inhibiting GH release. JAK-STAT signalling belongs to the growth hormone receptor itself, not to GHRH, which eliminates option D. This duality produces the ultradian pulsatility of GH observed clinically.

Reference: Ganong Review of Medical Physiology, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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