The response in spinal bone mass to Tibolone treatment is related to bone turnover in elderly women

To determine the ability of bone turnover to predict the response in bone mass during treatment with Tibolone, two biochemical markers of bone metabolism were evaluated [CrossLaps TM corrected for urinary creatinine (Cross-Laps TM/Cr.) and serum osteocalcin measured in a newly developed assay (N-Mid)]. Data from a 2-year double-blind, randomized trial with 56 completing Tibolone-treated women and 13 placebo-treated women were studied. Bone mineral density in the spine (QDR-1000) and indices of bone turnover were determined every 3 months throughout the study. The response in bone mass was calculated as the percent annual change in bone mineral density from baseline and was determined from a total of nine measurements. The response in bone mass was correlated to prestudy values of CrossLaps TM/Cr. ( r = 0.27; p < 0.05), but was uncorrelated to prestudy values of N-Mid. The changes from baseline of these two markers were significantly correlated with the response in bone mass from the 6 months' time point and throughout the rest of the study, i.e., at 1 year: CrossLaps TM/Cr.: r = 0.54; p < 0.001, N-Mid: r = 0.49; p < 0.001). The change from baseline in the two markers was clearly more predictive of the response in bone mass than the baseline values of these markers as evaluated in a multiple, linear regression-model. Within 1 year of Tibolone-treatment, measured changes in CrossLaps TM/Cr. and bone mineral density are at least equally predictive of the true response in bone mass over 2 years. These results indicate a possibility of monitoring Tibolone therapy with biochemical markers of bone turnover, at least on group basis.