Clinical usefulness of markers of bone degradation and formation.

The evaluation and management of patients with metabolic bone disease has been enhanced in recent years by the availability and clinical application of new biochemical markers of bone degradation and bone formation. Traditionally, biochemical markers such as serum alkaline phosphatase activity and urinary hydroxyproline measurements have been used to facilitate the clinical monitoring of patients receiving therapy for metabolic bone diseases like Paget's disease and osteomalacia. The poor specificity and sensitivity of these older markers however, made it difficult to follow patient response to therapy with the more subtle bone diseases like osteoporosis and metastatic bone cancer. New advances in bone marker biology particularly with biochemical markers of bone resorption have renewed interest in the use of biochemical markers to manage patients with different forms of metabolic bone disease. Bone loss markers such as the pyridinium cross-links and associated telopeptides have expanded the application of bone markers to not only monitor therapy in patients with metabolic bone disease but to reliably predict the bone density response to anti-resorptive medications. These markers have also been used to identify patients at risk for fractures who have significant bone density loss as a result of bone disease or as a physiologic consequences of menopause. This report reviews the relevant, newer markers of bone turnover and their current clinical utility in patients with osteoporosis and metastatic bone disease.