Biochemical markers of bone turnover: an update.

Currently, biomarkers are available which have considerably increased the possibility of monitoring changes in bone turnover. Assays for carboxy-terminal procollagen I fragments, osteocalcin and the bone-specific isoenzyme of alkaline phosphatase allow a more precise assessment of the complex osteoblastic functions in health and disease; osteocalcin appears at present to be the most satisfactory one. With respect to bone resorption, the measurement of urinary pyridinoline cross-links seems to be the most reliable assay. It has to be emphasized, however, that a single biomarker may be of value in some metabolic bone diseases but not in others.