Creatinine clearance systematically overestimates true GFR. What is the reason?

• A Creatinine is reabsorbed in the proximal tubule
• B Creatinine is secreted by the proximal tubule into the tubular lumen ✓
• C Creatinine undergoes tubular synthesis from arginine
• D Creatinine is freely filtered but binds plasma proteins

Explanation

Creatinine is mostly cleared by filtration, but a small amount is actively secreted by proximal tubular cells via organic cation transporters. This adds to urinary excretion beyond what filtration alone delivers, inflating the calculated clearance above actual GFR. Reabsorption would cause underestimation, not overestimation, and creatinine is neither synthesized by the tubule nor significantly protein bound.

Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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