Serum and urinary markers of bone remodeling: assessment of bone turnover.

It appears that at present, serum BGP is the one bone protein that has the most promise for assisting in the diagnosis and management of high turnover metabolic bone disease states. If further studies confirm its usefulness in osteoporosis as a predictor of rapid bone loss without the need for bone biopsy, this serum marker will then not only allow early detection but also an appropriate choice of therapy in osteoporosis, i.e. the use of specific inhibitors of high turnover states such as estrogen, calcitonin, or bisphosphonates. In addition, it may also permit more accurate follow-up of patients suffering from diseases such as primary hyperparathyroidism after surgery. In low turnover osteoporosis, it may also serve a useful function to observe whether the osteoblast can be stimulated to enhance bone formation with therapies such as fluoride, anabolic steroids, PTH, etc. As yet, additional measurements, such as bone histomorphometry and other bone mineral markers, are required for definitive diagnosis. Hopefully, the availability of specific well-characterized antibodies against BGP may define its role more accurately. Recently, several other new bone proteins have been identified but at present they have very limited clinical application. Future studies into the structure-function relationship of these bone proteins may identify those markers which will be most relevant to the diagnosis and treatment of metabolic bone disease.