Eating disorders and their effects on bone health

Abstract

Low-weight eating disorders such as anorexia nervosa (AN) are associated with low bone density, impaired bone structure, and a higher risk for fracture in both adults and adolescents. Factors contributing to low bone density include changes in body composition, hypogonadism, a state of acquired growth hormone resistance with low insulin-like growth factor-1 (IGF-1) levels, relative hypercortisolemia, and changes in other hormones that may impact bone metabolism including leptin, peptide YY, oxytocin, adiponectin, insulin, and amylin. The best strategy to improve bone density and bone accrual rates is weight gain and restoration of menstrual function; however, residual deficits often persist. In addition, a significant number of patients remain low weight for many years. Calcium and vitamin D status should be optimized; however, supplementation of these micronutrients alone is not effective in improving bone density. Physiologic estrogen replacement is effective in increasing bone density at the spine and hip in girls with anorexia nervosa (AN) such that bone accrual rates approximate that in normal-weight controls; however, catch-up does not occur. Bisphosphonates (anti-resorptive) are effective in increasing bone density in adults, but not adolescents with AN. IGF-1 is a bone anabolic hormone, and IGF1 replacement increases bone formation in adolescents, and with estrogen increases bone density in adults with AN. More studies are necessary to determine the best strategies to optimize bone density in AN.