Adolescents with anorexia nervosa (AN) are at high risk for low bone mineral density at a time when healthy adolescents are rapidly accruing bone, with implications for peak bone mass and fracture risk in later life. They are also deficient in insulin-like growth factor 1 (IGF-1), the bone trophic factor made in the liver in response to growth hormone (GH), despite elevated levels of GH. It is possible that deficiency of IGF-1, a hormone very important for the maintenance of skeletal integrity, may contribute to the severe osteopenia seen in AN. The physiologic effects of rhIGF-1 treatment in adolescents with AN have not been studied. The goal of this proposal is to investigate the effects of rhIGF-1 on bone density and bone microarchitecture in adolescent girls with AN over a 6 month period. We hypothesize that adolescent AN patients, being IGF-1 deficient, will respond to exogenously administered rhIGF-1 with elevations in biochemical indices of bone turnover and an increase in bone density and improvement in bone structure.