Parathyroid hormone produces a prompt phosphaturic effect. Which transporter does PTH remove from the apical membrane of the proximal tubular cells to achieve this?

• A NCC sodium-chloride cotransporter
• B SGLT2 sodium-glucose cotransporter
• C Sodium-phosphate cotransporter (NaPi-IIa/IIc) ✓
• D ENaC epithelial sodium channel

Explanation

PTH binds receptors on proximal tubular cells and, via cAMP-dependent mechanisms, causes internalization of the type IIa and IIc sodium-phosphate cotransporters from the brush border membrane. Phosphate reabsorption therefore falls sharply, producing phosphaturia and lowering serum phosphate. In the same hormone action, PTH simultaneously enhances calcium reabsorption in the distal tubule, which distinguishes its renal profile from that of FGF23.

Reference: Williams Textbook of Endocrinology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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