Clinical use of serum and urine bone markers in the management of osteoporosis.

Osteoporosis is a common disease characterized by decreased bone mass, increased bone turnover, and increased susceptibility to fracture. Almost 44 million Americans are estimated to have low bone mass, which puts them at increased risk of developing osteoporosis and fractures. Osteoporosis is diagnosed by a low bone density (BMD) measurement, because a low BMD is known to contribute to increased fracture risk, which is the main source of morbidity and mortality for osteoporosis. However, changes in bone mass and density in response to anti-resorptive therapy account for only a small portion of the predicted fracture risk reduction. Whereas dynamic changes in bone turnover, estimated by measurement of bone biochemical markers, such as breakdown products of type-I collagen and proteins secreted by osteoblasts and osteoclasts in blood and urine, can account for a major portion of anti-fracture efficacy of anti-resorptive agents. Most anti-resorptive agents act by rapidly reducing bone markers. This has led to advocacy for use of bone turnover markers, in complement to BMD measurement, in the management of osteoporosis. In general, higher bone turnover is associated with accelerated bone loss and potential deterioration in bone quality. Several clinical trials have established the potential utility of markers to identify patients with rapid bone loss, to aid in therapeutic decision-making, and to monitor therapeutic efficacy of various treatments. Elevated marker levels have been shown to be associated with increased risk of fracture in elderly women, but their utility in predicting fracture is not yet established. In this article, we provide a brief summary to primary practitioners about the role bone markers can play in the management of osteoporosis.