## 3 Results
### Findings from the Subgroup Analyses  
All data of the subgroup analyses results are collected in Supplementary Data 2 (Tables S2-S5). All the original forests of the subgroup analyses are shown in Supplementary Data 3. The correlations between the baseline BTMs and BMD changes underwent a subgroup analysis by a group of BTMs. According to the results of the subgroup analyses, we found that the baseline procollagen type I N propeptide (PINP) values were moderately and positively correlated with the BMD changes (COR\({}_{\text{PINP}}\) = 0.42, 95% CI: 0.34-0.50, heterogeneity: I\({}^{2}\) = 0%, \(p\) = 0.4), while the correlations between other BTMs and BMD changes were lower than 0.4, indicating that the other baseline BTMs and the BMD changes were poorly correlated. The results of the subgroup analyses on the correlation between the changes in BTMs and BMD were collected in Figure 6 and grouped by bone sites, intervention, the time duration of BTMs measurements, and the time duration of BMD measurements, respectively. Figure 6a shows the results of subgroup analyses by a group of bone sites, in which the biomarker of U-NTX was moderately correlated with total body BMD changes (COR = \(-\)0.44, 95% CI: \(-\)0.58 to \(-\)0.29; heterogeneity: I\({}^{2}\) = 43%, \(p\) = 0.18). Figure 6b showed the subgroup results by group of intervention. In Figure 6b, the changes in PINP and BMD under denosumab intervention were moderately correlated (COR = \(-\)0.44, 95% CI: \(-\)0.57 to \(-\)0.31; heterogeneity: I\({}^{2}\) = 0%, \(p\) = 0.71). Figure 6c presented the results of subgroup analyses grouped according to the time duration of BTMs measurement, from which we could conclude that the changes of OC and UNTX from baseline to the 12 th month after drug intervention were moderately associated with the BMD changes (COR\({}_{\text{OC}}\) = \(-\)0.46, 95% CI: \(-\)0.59 to \(-\)0.30, heterogeneity: I\({}^{2}\) = 0%, \(p\) = 0.73; COR\({}_{\text{UNTX}}\) = \(-\)0.43, 95% CI: \(-\)0.61 to \(-\)0.21, heterogeneity: I\({}^{2}\) = 57%, \(p\) = 0.13, respectively). Finally, Figure 6d showed the results of subgroup analyses grouped according to the time duration of the BMD measurement; in Figure 6d, we could see that the changes of U-NTX were moderately correlated with the BMD changes from baseline to the 48 th month after drug initiation (COR = \(-\)0.52, 95% CI: \(-\)0.64 to \(-\)0.21, heterogeneity: I\({}^{2}\) = 0%, \(p\) = 0.82). Figure 1: Flow chart of the literature search and study selection. Figure 2: Quality assessment of the eligible studies. (**a**) Summary of the quality of the randomized controlled trials; (**b**) Summary of the quality of the nonrandomized trials. Figure 4: _Cont._  
Figure 3: Significant correlations between baseline bone turnover markers (BTMs) and bone mineral density (BMD) changes at different bone sites under different drug interventions over time. (**a**) Correlations between baseline BFMs and BMD changes from baseline at different bone sites under different drug interventions over time. (**b**) Correlations between baseline BFMs and BMD changes from baseline under different drug interventions over time. BFM bone formation marker, BRM bone resorption marker, ALN alendronate, ALN5 mg/d ALN, ALN10 10 mg/d ALN, ALN10+HRT, combination of 10 mg/d ALN and HRT, HRT hormone replacement therapy, TPTD teriparatide, FN femoral neck, LS lumbar spine, TB total body, TH total hip, TR trochanter. Figure 4: Significant correlations between the changes in BEMs and BMD at different bone sites under different drug interventions over time. (**a**) Correlations between the changes in bone ALP and BMD from baseline at different bone sites under different drug interventions over time. (**b**) Correlations between the changes in osteoclast (OC) and BMD under different drug interventions over time. (**c**) Correlations between the changes in procollagen type I N propeptide (PINP) and BMD under different drug interventions over time.