In order to investigate the effects of lovastatin on adrenal and gonadal function, we prospectively determined the basal and gonadorelin-stimulated concentrations of testosterone, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) and the cortisol response to adrenocorticotropic hormone (ACTH) in a sample of 25 male patients with advanced chronic renal failure, hypercholesterolemia and proteinuria. Hormone studies were done prior to and after lovastatin treatment. The values of these patients were compared with those of a matched healthy control group. Before starting treatment with lovastatin, the patients showed significantly lower testosterone concentration and higher LH concentration than the control group. After stimulation with gonadorelin, they also showed a lower increase in testosterone and LH. After 12 months of lovastatin treatment, a significant decrease in the concentration of cholesterol, LDL C, VLDL C and apo B was observed, but neither the basal testosterone concentration nor the response to gonadorelin stimulation was modified. Before treatment, basal and ACTH-stimulated serum cortisol levels did not differ from those of the control group. After lovastatin treatment, neither the basal serum cortisol levels nor the response to ACTH was modified. We conclude that in the patients studied, although the decrease in testosterone concentration may be partially attributable to a decrease in its synthesis, lovastatin treatment does not increase testosterone deficit. This is either because this drug does not inhibit gonadal hydroxymethylglutaryl CoA reductase at the does given or because the cholesterol which LDL C provides the cell with is enough to maintain testosterone synthesis.