Young women with anorexia nervosa (AN) have subnormal levels of dehydroepiandrosterone (DHEA) and estrogen that may be mechanistically linked to the bone loss seen in this disease. The purpose of this study was to compare the effects of a 1-yr course of oral DHEA treatment vs. conventional hormonal replacement therapy (HRT) in young women with AN. Sixty-one young women were randomly assigned to receive oral DHEA (50 mg/d) or HRT (20 micro g ethinyl estradiol/0.1 mg levonorgestrel). Anthropometric, nutrition, and exercise data were acquired every 3 months, and bone mineral density (BMD) and body composition were measured by dual energy x-ray absorptiometry (DXA) every 6 months over 1 yr. Serum samples were obtained for measurements of hormones, proresorptive cytokines, and bone formation markers, and urine was collected for determinations of bone resorption markers at each visit. In initial analyses, total hip BMD increased significantly and similarly (+1.7%) in both groups. Hip BMD increases were positively correlated with increases in IGF-I (r = 0.44; P = 0.030) and the bone formation marker, bone-specific alkaline phosphatase increased significantly only in the DHEA treatment group (P = 0.003). However, both groups gained significant amounts of weight over the year of therapy, and after controlling for weight gain, no treatment effect was detectable. There was no significant change in lumbar BMD in either group. Both bone formation markers, bone-specific alkaline phosphatase and osteocalcin, increased transiently at 6-9 months in those subjects receiving DHEA compared with the estrogen-treated group (P < 0.05). Both DHEA and HRT significantly reduced levels of the bone resorption markers, urinary N-telopeptides (P < 0.05). There was a positive correlation between changes in IGF-I and changes in weight, body fat determined by DXA, and estradiol for both groups. In addition, patients receiving DHEA exhibited improvement on three validated psychological instruments (Eating Attitudes Test, Anorexia Nervosa Subtest, and Spielberger Anxiety Inventory). Both DHEA and HRT had similar effects on hip and spinal BMD. Over the year of treatment, maintenance of both hip and spinal BMD was seen, but there was no significant increase after accounting for weight gain. Compared with HRT, DHEA appeared to have anabolic effects, evidenced by the positive correlation between increases in hip DXA measurements and IGF-I and significant increases in bone formation markers. Both therapies significantly decreased bone resorption. Replicating results from studies of the elderly, DHEA resulted in improvements in specific psychological parameters in these young women.