The specific aims of this study is as follows: Specific Aim 1. Androgen deficiency is common in anorexia nervosa, and its pathophysiologic basis is suppression of overian androgen production. The investigators will investigate in women with anorexia nervosa: A. Whether androgen defiiciency is common in women with anorexia nervosa. B. The pathogenesis of androgen deficiency and determine whether ovarian and/or adrenal androgen production is reduced. Specific Aim 2. Physiologic testoerone replacement increases markers of bone formation and has a short-term anabolic effect on lean body mass. The investigators will investigate in women with anorexia nervosa whether: A. Relative tesstosterone-deficiency contributes to osteopenia. B. Short-term administration of physiologic testosterone increases bone formation markers. C. Short-term administration of physiologic testosterone increases lean body mass. Specific Aim 3. Physiologic testosterone replacement increases bone density. The investigators will investigate in women with anorexia nervosa: A. Long-term effects of androgen-deficiency on bone mass and whether physiologic testosterone administration is the first successful intervention to increase bone density in anorexia nervosa. B. Whether the effects of androgens on bone density are sustained after discontinuation of the hormonal therapy. C. Whether bone turnover markers can be used to predict changes in bone density as a result of testosterone administration. D. The effects of testosterone administration on lean body mass in an estrogen replete model.