Osteoporosis is a systemic progressive bone disease, in which the bone mass gradually decreases over time resulting in the loss of bone strength. The bones become fragile, and the risk of fractures increases. The main pathobiochemical cause of osteoporosis is disrupted phosphorus-calcium metabolism. The process of synthesis and decomposition of bone tissue is carried out by specialized bone cells – osteoblasts and osteoclasts. Osteoblasts participate in the synthesis of a new bone substance, whereas osteoclasts destroy it. Normally this system is in equilibrium, which means that new cells are synthesized to replace the destroyed cells (1).

Bone mineral density (BMD) is a test used by health care providers to examine segments of bone tissue through X-rays in order to detect or rule out osteoporosis. According to WHO criteria, osteoporosis is present if a value of BMD, measured by dual-energy X-ray absorptiometry (DXA) on the spine or hip, more than 2.5 SD below the normal peak values for young adults (T-score < ?2.5) (1).

Though, BMD measurement serves as a pivotal mainstay in the decision to initiate an anti-resorptive treatment and the test is widely used to monitor treatment efficacy, BMD alone isn’t enough for the treatment monitoring. A new tool allowing to detect the dynamics of bone remodeling with respect to bone formation and resorption is molecular markers of bone metabolism. A variety of reliable, cost-effective, sensitive bone turnover markers (BTMs) complement the measurement of BMD, which is current gold standard test for the diagnosis of osteoporosis. BTMs are especially effective in the management of osteoporosis, and particularly in the follow-up of those individuals who have been on antiresorptive or bone formation therapies (2).

BTMs are biochemical materials which levels are measured in blood and urine, and then their values are used to examine the metabolic activity of bone tissue. Markers do not have any part in controlling skeletal metabolism. BTMs are divided into formation and resorption markers. Osteoblastic cells produces bone formation turnover or it may be even derived from procollagen metabolism. The degradation products of collagen or osteoclasts are the resorption markers (2).

Not only BTMs are helpful in assessing of the ongoing bone remodeling but also provide pharmacodynamic information on the therapeutic response to osteoporosis medications, therefore are essential for the optimization of therapy. MTMs are particularly useful in assessing the patient's compliance to osteoporosis medication, where drug compliance can be a big issue. Monitoring compliance and adherence to treatment is especially important in the case of bone resorption inhibitors (2).

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