Therapies are still being sought for the prevention of loss of body weight and lean body mass in HIV disease. The purpose of the present study was to identify a serum marker that would help in selecting patients who may be appropriate candidates for the use of anabolic agents, such as growth hormone, to restore lean body mass. This study included 26 HIV-infected patients and nine healthy controls, assessed previously for the effectiveness of 2 weeks of growth hormone administration in the stimulation of protein synthesis in skeletal muscle. Serum levels of interleukins-1beta, -6 and -10 were not useful predictors of the anabolic response to growth hormone. Serum concentrations of tumour necrosis factor alpha (TNFalpha) were significantly elevated (P<0.05) in patients with AIDS and AIDS-related weight loss, and there was a significant correlation between the serum concentration of interleukin-1 receptor antagonist and stage of disease (P=0.03). However, the serum concentration of the soluble TNFalpha receptor type 2 was most predictive of an inability of muscle protein synthesis to respond anabolically to growth hormone (r=-0.42, P=0.01). These data suggest that inflammation impacts on the responsiveness of muscle tissue to an anabolic stimulus, and that the soluble TNFalpha receptor type 2 provides a useful serum marker for metabolic dysfunction in HIV disease, which can be used to identify individuals likely to respond to growth hormone-based anabolic therapy.