Early changes in biochemical markers of bone turnover predict bone mineral density response to antiresorptive therapy in Korean postmenopausal women with osteoporosis

Biochemical markers of bone turnover have been suggested to be useful in monitoring the efficacy of antiresorptive therapy. In this study, we investigated the predictive value of bone turnover markers to determine short-term response in bone mineral density (BMD) and to identify norresponders in 138 postmenopausal women (mean age 58 years) with osteoporosis given with either hormone thearpy (HT) or alendronate. Urinary type I collagen N-telopeptide (NTx) and serum osteocalcin (OC) at baseline, 3, and 6 months after treatment as well as spine and femoral neck BMD at baseline and 12 months were measured. Significant decreases in both NTx and OC were evident in women on treatment with antiresorptive agents as early as 3 months (p < 0.01). Percent change of NTx at 3 months correlated with the percent change of spinal BMD at 12 months of treatment. When bone turnover markers were stratified by tertiles, the average rate of lumbar spine BMD gain increased significantly with increasing tertiles of baseline value (p < 0.05) and percent change (p < 0.05) of urinary NTx at 3 month of treatment. In terms of BMD response, urinary NTx at 3 months decreased significantly more in BMD responders group than in nonresponders group. Logistic regression analysis demonstrated that percent change of NTx at 3 months is an independent predictor to identify BMD non responders, defined as those whose BMD gain remained within the precision error range of dual energy X-ray absorptiometer (DXA). We conclude that biochemical markers of bone turnover, especially percent change in urinary NTx levels, can be used to determine BMD response to antiresorptive therapy in Korean postmenopausal women with osteoporosis.