Growth hormone releasing hormone (GHRH) binds to its receptor on somatotrophs. Which intracellular second messenger system is primarily activated by GHRH receptor binding to stimulate both GH synthesis and secretion?

• A Phospholipase C (PLC) / IP3-DAG pathway
• B Receptor tyrosine kinase / MAPK pathway
• C Adenylyl cyclase / cAMP-PKA pathway ✓
• D Guanylyl cyclase / cGMP pathway

Explanation

The GHRH receptor is a G-protein coupled receptor (Gs) that activates adenylyl cyclase, increasing intracellular cAMP and activating protein kinase A (PKA). This pathway stimulates both GH gene transcription and GH exocytosis. The PLC pathway is used by TRH and GnRH receptors. Receptor tyrosine kinases are used by growth factors like IGF-1.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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