Chapter 14 - Markers of Bone Remodeling and the Aging Skeleton

Abstract

Biochemical markers of bone turnover, i.e markers of bone formation and bone resorption, can be measured easily and non-invasively in serum and urine. In postmenopausal women and men, accelerated bone turnover (as measured by markers of bone formation and/or resorption) has been shown to be associated with increased fracture risk independent of bone mineral density (BMD) or clinical risk factors. Furthermore, as changes in bone turnover markers in response to therapeutic interventions occur much more rapidly than changes in BMD, bone markers may be useful in the monitoring of treatment, e.g., to evaluate treatment efficacy or patient compliance. One of the reasons why bone turnover markers are useful in assessing fracture risk and therapeutic efficacy is their ability quantitatively to reflect the actual rate of, and changes in, skeletal remodeling. However, the simplicity, convenience and clinical sensitivity of these markers need to be balanced against a rather high degree of variability that introduces substantial “background noise.” This latter fact is of particular relevance when it comes to the assessment of bone turnover in individual patients as opposed to the study of larger groups, e.g., in clinical trials. For an appropriate interpretation of any bone marker measurement, it is therefore important to identify pre-analytical (biological) and analytical (technical) factors that may affect variability. This chapter focuses on age-related changes in markers of bone turnover in men, including their response to pharmacological interventions.