Clinical Significance of Bone Turnover Markers in Osteoporosis: Fracture Risk Assessment and Treatment Monitoring

Osteoporosis is a systemic skeletal disorder characterized by compromised bone strength and a higher risk of fractures. Although bone mineral density (BMD) remains the primary diagnostic measure, it has several limitations, including delayed detection of therapeutic response, restricted measurement sites, and limited sensitivity to predict fracture risk accurately. Bone turnover markers (BTMs) are noninvasive indicators of bone remodeling that are increasingly being used as complementary tools in osteoporosis assessment. Among them, serum procollagen type I N-terminal propeptide and C-terminal telopeptide of type I collagen are reference markers of bone formation and resorption. However, BTM levels can be influenced by biological and pathological factors, including circadian rhythms, food intake, and assay variability, thereby limiting their routine use as predictive markers. In individuals at risk of fracture, antiresorptive agents such as bisphosphonates and denosumab cause rapid alterations in BTMs, which correlate with long-term gains in BMD and reduced fracture risk. Monitoring BTMs can help evaluate therapeutic efficacy and adherence and complement BMD measurement in fracture risk prediction. Overall, rather than being used as stand-alone diagnostic markers, BTMs should be used as complementary tools for monitoring therapeutic responses and supporting fracture risk assessment.