Insufficient estrogen can cause osteoporosis in young female athletes, like the 17-year-old runner described here, as well as in postmenopausal women, whose management is also detailed. The most common technique for diagnosis is dual-energy x-ray absorptiometry. Prevention and treatment depend on a woman's age but may include increased calcium intake, weight gain, weight-bearing and resistance exercise, and estrogen replacement therapy. Alendronate and/or calcitonin may be used as alternatives to estrogen therapy.