The published reports concerning serum levels of sex hormone binding globulin (SHBG) in women with anorexia nervosa are few in number and controversial. Indeed, very little is known of the factors influencing SHBG concentrations in these patients. In an attempt to clarify this problem we evaluated serum levels of SHBG, estradiol, testosterone, luteinizing hormone, follicle stimulating hormone, triiodothyronine, thyroxine, their free fractions and insulin in 19 women with anorexia nervosa. Plasma glucose levels, total protein, triglycerides and cholesterol were also studied. Seven healthy women with normal weight and regular menstrual cycles served as controls. The serum concentrations of SHBG in patients with anorexia nervosa (165.27 +/- 63.5 nmol/l) were significantly higher (p < 0.01) than those in the control group (96.21 +/- 38.04 nmol/l), but the levels of estradiol, testosterone, free triiodothyronine and the ratio of testosterone to SHBG were significantly lower. An inverse correlation between SHBG and body weight (r = -0.761) was found in the patients. The alterations in SHBG concentrations were not associated with the changes in testosterone, gonadotropins, thyroid hormones and biochemical parameters. These findings suggest that body weight is one of the more important factors influencing the SHBG concentrations in women with anorexia nervosa.