Slide 1: Attention Trivia Buffs! What popular dietary supplement commonly used by athletes can result in serum creatinine elevation without actually affecting the GFT?

Slide 2: Answer: Creatine! Creatine is a nitrogenous acid found in skeletal muscle. The phosphorylated version, phosphocreatine, donates a phosphate group for the quick regeneration of ATP after exercise. [diagram]

Slide 3: Creatine supplementation is associated with faster recovery times and improved performance in athletes who perform short-duration high-intensity exercise, but not endurance sports. It works by accelerating the regeneration of creatine phosphate during the exercise recovery phase.

Slide 4: Because creatine is metabolized into creatinine before being excreted, creatine supplementation increases serum creatinine, resulting in a picture of “pseudo renal failure.” Athletes not taking creatine may also have falsely elevated creatinine due to skeletal muscle hypertrophy and increased endogenous creatine production. [diagram]

Slide 5: In patients suspected to have pseudo renal failure, a serum cystatin C level may be a more accurate estimator of GFR than serum creatinine. Cystatin C is produced in all nucleated cells, not just skeletal muscle.

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