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.
- Graham AS, Hatton RC. Creatine: a review of efficacy and safety. J Am Pharm Assoc (Wash). 1999 Nov-Dec;39(6):803-10; quiz 875-7. PMID 10609446
- Williamson L, New D. How the use of creatine supplements can elevate serum creatinine in the absence of underlying kidney pathology. BMJ Case Rep. 2014 Sep 19;2014. PMID 25239988
- American College of Physicians MKSAP 18: Medical Knowledge Self-Assessment Program.
Tags: creatine, creatinine, dietary supplement, nephrology, renal