Osteopenia.

Osteopenia in the elderly is responsible for 1.3 million fractures per year in the United States. The acute care costs associated with this disorder are between $6 and $10 billion dollars annually. Although much has been learned over the last few years of the factors that predispose patients to osteoporosis and how these factors may be avoided, the precise pathophysiologic mechanisms for bone loss remain obscure. Significant technological advances have been made in the 1980s in the development of noninvasive methods for measuring bone mineral density that give indirect assessments of bone mass. However, these methods are very controversial, are not suitable for mass screening for detecting subjects potentially at risk, and have a limited place in routine clinical care. Osteoporosis is characterized by thinning and fragmentation of trabecular bone, which is probably irreversible when it is far advanced. The most reasonable therapeutic approach may be prevention, which can be achieved in many patients by estrogen therapy in the perimenopausal years and insuring an adequate dietary calcium intake, particularly in adolescents and in the elderly. Physical activity throughout life is also likely to be important in maintaining adequate bone mass. It is important to differentiate osteoporosis from other causes of osteopenia, for example, osteomalacia, primary hyperparathyroidism, and malignant diseases such as myeloma, since these bone diseases have a different natural history, pathophysiology, and treatment.