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 microM) than in amateur (75 microM; P < 0.001) and professional cyclists (72 microM; 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.