THE VALUE OF BIOCHEMICAL MARKERS OF BONE TURNOVER IN OSTEOPOROSIS

A number of biochemical markers of bone turnover have been described a nd these reflect the activity of osteoblasts (bone formation) or osteo clasts (bone resorption). These markers have the following advantages for the measurement of bone turnover: (1) they are noninvasive; (2) in expensive; (3) can be repeated on many occasions; (4) and reflect bone cell activity in the entire skeleton. They have disadvantages: (1) th ey do not provide information about the work of individual cells; (2) they do not reflect the process of mineralization; and (3) their level s may be affected by the rate of clearance. The markers have been used to study the pathogenesis of osteoporosis, identify postmenopausal wo men with accelerated bone loss, predict fracture independently of bone loss, predict response to therapy, and monitor response to therapy. T hey may also be useful in the setting of clinical trials for choosing minimal and maximal effective doses, understanding the mechanism of th e changes in bone mineral density (BMD) and studying the effect and ti me course of changes in bone after cessation of therapy. Markers do no t provide a surrogate for fracture risk or BMD. However, they do have uses in osteoporosis and can provide preliminary data in the short ter m that can be used in the design of longterm studies of BMD and fractu re.