Glomerular filtration rate in endurance athletes

OBJECTIVE: The interpretation of biochemical testing in sportsmen requires caution. Although creatinine-based estimates of glomerular filtration rate (GFR) overcome some shortcomings of serum creatinine, there is scarce information on their use in endurance athletes. DESIGN: We evaluated GFR, estimated by the recommended Modification of Diet in Renal Disease (MDRD) equation in athletes. PARTICIPANTS: Seventy-six professional male cyclists, 71 amateur male cyclists, and 65 healthy sedentary matched controls were included in the study. RESULTS: The mean serum creatinine level was significantly higher in the sedentary subjects (81 μM) than in amateur (75 μM; P <0.001) and professional cyclists (72 μM; P <0.001), and it was also marginally higher in amateur than in professional cyclists (P = 0.049). The mean estimated GFR value increased throughout the three subgroups, being significantly lower in the sedentary population (98 mL·min·[1.73 m]) than in the subgroups of amateur (109 mL·min·[1.73 m]; P <0.001) and professional cyclists (113 mL·min·[1.73 m]; P <0.001), but it did not differ between amateur and professional cyclists (P = 0.116). The average intensity of daily physical exercise, but not the body mass index, was inversely associated with serum creatinine and positively associated with the estimated GFR. CONCLUSIONS: The MDRD equation should be used with caution in athletes, and it should consider intensity and type of physical exercise.