Which single property makes inulin the gold standard marker for measuring glomerular filtration rate?

• A Its clearance varies directly with plasma concentration
• B It is secreted by the proximal tubule at a constant rate
• C It is completely reabsorbed by the proximal tubule
• D It is freely filtered and neither reabsorbed nor secreted by the tubules ✓

Explanation

Inulin is a small fructose polymer that crosses the glomerular filter freely and then undergoes no tubular transport in either direction. Its clearance therefore equals the true volume of plasma filtered per minute. Creatinine fails this standard because it undergoes some proximal tubular secretion, so its clearance slightly overestimates GFR. Para-aminohippurate is actively secreted, making its clearance a measure of renal plasma flow rather than GFR.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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