Osteoporotic stress fractures in anorexia nervosa: etiology, diagnosis, and review of four cases.

Anorexia nervosa (AN) is a chronic eating disorder characterized by self-imposed semi-starvation that affects 1% of adolescent females. AN predisposes to osteoporosis through hypothalamic dysfunction, which may lead to elevated cortisol as well as diminished estrogen and progesterone. The osteoporosis associated with AN affects both trabecular and cortical bone and increases the risk of osseous fracture. Fractures in this population may go unrecognized, because planar X-rays may be nondiagnostic for 6 weeks or more. Four women with AN ranging in ages from 22 to 34 with skeletal pain and nondiagnostic roentgenographs are described. Stress fractures in these patients were subsequently identified by bone scan. Although moderate exercise in patients with AN-associated osteoporosis may be beneficial, strenuous exercise can be detrimental, with its potential risk of stress fractures and exacerbation of the underlying neurohormonal abnormalities. This risk for fracture may persist well after improvement in the patient's AN.