**3. Research progress in bone turnover markers**

The diagnosis of osteoporosis also requires etiological diagnosis to further distinguish primary or secondary [59]. Bone turnover markers provide an important reference for clinical differential diagnosis and treatment follow-up. Bone tissue continuously undergoes bone modeling and bone remodeling to maintain bone growth and structural integrity. The microenvironment is characterized by continuous absorption of old bone to form new bone. This self-renewal process is called bone turnover (bone turnover). Bone turnover biomarkers (BTMs) are biochemical markers released in blood or urine during bone remodeling, which can reflect the dynamic changes of whole body bone tissue earlier than bone density. Including biochemical markers of bone formation and bone resorption, the former reflects the activity of osteoblasts and the state of bone formation, and the latter represents the activity of osteoclasts and the level of bone resorption. The determination of these markers is helpful for identifying primary and secondary osteoporosis, judging the type of bone turnover, predicting the rate of bone loss, assessing fracture risk, understanding disease progression, selecting interventions, monitoring drug efficacy and compliance, etc.

The common clinical biochemical markers of bone metabolism are shown in the table below (**Table 3**). Among the above markers, the International Osteoporosis Foundation (IOF) and International Federation of Clinical Chemistry (IFCC) have recommended serum P1NP and CTX-1 as bone formation and resorption reference markers, which have the characteristics of good sensitivity, high specificity, good repeatability, and economical application. In recent years, with the deepening of research and the development of biotechnology, the research on bone metabolism markers has made great progress. New markers such as Periostin, advanced glycation end products/receptor for advanced glycation end products (AGEs/RAGE), gelsolin, annexin A2 etc. gradually emerged, which has potential advantages in reflecting the dynamic changes of the whole body bone tissue.


**Table 3.**

*Common clinical biochemical markers of bone turnover.*
