We compared the metabolic effects of recombinant human (rh) insulin-like growth factor (IGF)-1 or a combination of rhIGF-1 + rh growth hormone (GH) on resting energy expenditure (REE) in 8 maintenance hemodialysis (MHD) patients. Seven males and 1 female (aged 41.6 +/- (SD) 12.4) with no evidence of malnutrition (BMI 21.6 +/- 2.2 kg/m2, serum albumin 45 +/- 2 g/l, serum IGF-1 359 +/- 165 microg/l) received either rhIGF-1 (80 microg/kg/day) or rhIGF-1 (80 microg/kg/day) + rhGH (50 microg/kg/day) for 3 days in a random crossover design. REE and the respiratory quotient (RQ) were measured at rest before and after the 3-day treatment. The results confirmed that MHD patients have a REE not different from normal individuals. REE was strongly correlated with lean body mass but not with fat mass. rhIGF-1 treatment did not modify REE despite doubling serum IGF-1 values, whereas a combined rhIGF1 + rhGH treatment significantly increased REE by 11% (p < 0.001). There was no change in RQ under both treatments, in response to a proportionate increase in VCO2 and VO2. These results show that energy expenditure is mainly dependent upon lean body mass in well-nourished MHD patients. The metabolic effects of rhIGF-1 and rhGH on energy expenditure may differ in response to their opposite effects on lipid oxidation and insulin regulation.