CRF led to a reduction in muscle mass, which is found in 35 and 55% of patients, in some to a profound cachexia. A reduced fat free mass (FFM) is a factor associated with a poor tolerance to exercise and an halved survival. The exact causes and mechanisms leading to cachexia are not yet established. Recently, a chronic inflammatory condition has been quoted as a putative cause. This chronic inflammation would involve the molecular mechanisms leading to poor regulation of the balance of synthesis / protein degradation in muscle. A decrease in plasma and muscle amino acids was found among patients with a low FFM.. In addition, a decrease of plasma levels of some anabolic hormones, GH and androgens or IGF-1 has been found that could explain a lack of protein synthesis.