Determination of reference values of CTx and NMID-Osteocalcin and their association with osteoporosis in postmenopausal chilean women

Introduction: Bone densitometry (BD) has high specificity in the osteoporosis diagnosis but suboptimal sensitivity to estimate fracture risk. It was proposed that bone turnover markers (BTM) could be included in the osteoporosis risk algorithm, although the extent of its association is unknown. One recommended BTM to assess bone resorption is Beta-Cross Laps (B-CTx), while a BTM to assess bone formation is osteocalcin. Aims: To establish BCTx and N-MID osteocalcin (N-MID) ranges in postmenopausal women (PM) and compare BTM levels in two groups: control and with abnormal BD. Methods: PM with BD within the last year were recruited. A questionnaire of risk factors for fractures was applied, and BTM was measured. Volunteers with diseases that would affect bone remodeling were excluded. Results: 117 PM (57 control and 60 with abnormal BD) were recruited. 18% had osteoporosis, and the groups were comparable. The ranges for B-CTx and N-MID were 0.41 +/- 0.18 [IC95% 0.37-0.45] and 22.76 +/- 7.73 [IC95% 21.29-24.24] ng/mL. The mean levels of B-CTx and N-MID were higher in the group with abnormal BD (0.46 +/- 0.19 and 24.29 +/- 8.04 ng/mL). A moderate correlation between both BTM was found, but it was weak with abnormal BD. Conclusions: B-CTx and N-MID ranges were assessed for the first time in Chilean PM, similar to values found in other countries. Slightly higher values of BTM were found in the group with abnormal BD, which the presence of omitted secondary causes could explain. These BTM could be a complementary tool to BD and FRAX in bone evaluation.