60 patients (men, caucasians) with an estimated GFR between 60 and 15 ml/min/1.73m2 will be included in the study. After giving all necessary information and collection of informed consent, blood will be drown to allow creatinine, cystatin C, albumin, C reactive protein and urea dosages. GFR will be measured using plasmatic clearance of EDTA-51Cr. Body composition will be performed using DEXA scan. Two visits will be necessary to complete the evaluation for every patient, scheduled at the same time than the routine medical visits.