Bone Abstracts

Bone turnover markers (BTMs) are particularly useful in the early monitoring of the effectiveness of anabolic and antiresorptive therapy in osteoporosis and may help in the assessment of treatment compliance. How and when BTM levels change under antiresorptive or anabolic drugs is a key factor in assessing response to therapy. Thus, changes in BTM levels depend on the dose of the drug and the route of administration, and particularly on the mechanism of action. In this sense, responses to oral antiresorptive drugs may be assessed quickly, within 3 months, by measuring resorption markers, or later, when using formation markers. In the assessment of parenteral bisphosphonates and denosumab, changes in resorption markers are very fast. Bone markers, such as the cross-linked C-terminal and N-terminal telopeptides of type I collagen (sCTX and uNTX), are well positioned in clinical practice for monitoring antiresorptive treatment, and procollagen type I N-terminal propeptide (PINP) is the best marker for assessing response to teriparatide. In addition, BTMs may be useful in the monitoring of treatment discontinuation. When discussing bone markers in clinical practice, some interesting points arise: they may complement fracture risk assessment, and they may also help in the identification of secondary osteoporosis. The measurement of most bone markers by automated analysers has improved their laboratory reproducibility and accessibility. Practical considerations for the clinician when using BTMs include the awareness of the pre-analytical variability, taking care of precise timing and fasting status of the sample collection, in addition to other sources of pre-analytical variability, such as intercurrent diseases or recent fractures. In recent years, the technical advances in their determination, the use of appropriate reference intervals and the minimization of the sources of the pre-analytical variability have improved the performance of BTMs for assessing and treating patients with osteoporosis.