Nutritional markers such as lean body mass and serum albumin are strong predictors of the mortality and morbidity in patients with end-stage renal failure (ESRF) on maintenance hemodialysis (HD). Maintenance HD is considered to contribute to the malnutrition of patients with ESRF, but the exact mechanism has remained unknown. However, we have recently shown that the bioactivity of insulin-like growth factor-I (IGF-I) is reduced by 50% during HD. Furthermore, we showed that the reduction in the bioactivity of IGF-I is directly linked to an up-regulation of IGF-binding protein-1 (IGFBP-1), the only acutely regulated IGFBP, which increased by 6-fold during HD. IGFBP-1 is produced in the liver, primarily under the control of insulin, which promptly inhibits the hepatic production of IGFBP-1. As plasma insulin remains fairly low during a maintenance HD, the increase in IGFBP-1 may be explained by the absence of insulin.