Osteoporosis (“porous bone”) is a bone disease that increases the risk for fracture. It is caused by the loss of bone density from losing too much, not making enough, or a combination of both. Bone metabolism is the constant process of the body removing old bone (“bone turnover”) and replacing it (“bone resorption”). These processes take place in the osteoblasts, which form new bone, and osteoclasts, which break down old bone. As long as these processes are in balance, bone mass remains on a constant level.
At mid-life, individuals begin to lose bone quicker than they are able to replace it due to calcium metabolism, calcium and vitamin D deficiency, and hormonal factors, such as changes of estrogen level. Measuring proteins produced by the osteoblasts and osteoclasts provides a real-time evaluation of bone turnover, especially in the management of post-menopausal osteoporosis. Bone resorption markers can monitor progress of therapeutic interventions within a few weeks or months, whereas bone formation markers can take 6 to 12 months. This is still an improvement over bone mineral density (BMD), which can take as long as one to two years to determine the effectiveness of treatment.