Which biochemical marker is used to assess bone resorption in osteoporosis?

• A. Calcium
• B. Phosphorus
• C. Cross-linked C telopeptides
• D. Alkaline phosphatase

Answer: (C)

Bone resorption in osteoporosis is best assessed by measuring products released when bone collagen is broken down. When osteoclasts degrade type I collagen, fragments called cross-linked C telopeptides are released into the blood and urine, making them a direct and sensitive indicator of resorption activity. This is why this marker is the most appropriate choice for reflecting bone loss and for monitoring response to antiresorptive therapy. In contrast, calcium and phosphorus levels are influenced by many factors and don’t specifically quantify bone breakdown, while alkaline phosphatase reflects bone formation rather than resorption.