BACKGROUND Several factors associated with bone mineral density (BMD) increase are reported with daily teriparatide treatment, but there has been no systematic analysis to summarize these associations. The purpose of this study was to investigate the clinical determinants associated with BMD increase to daily teriparatide treatment. METHODS This was a retrospective study. We performed an analysis of 306 patients diagnosed with osteoporosis. Teriparatide was administered at 20μg/day for 12months. The primary efficacy measure was a change in lumbar spine (LS) BMD from baseline at 12months. To determine the response variables of BMD changes, we investigated the clinical determinants using univariate and multivariate analyses. RESULTS There was a 9.8±8.2% increase in LS BMD after 12months. Prior bisphosphonate treatment and baseline procollagen type I N-terminal propeptide (PINP) concentration were significantly associated with LS BMD absolute response by univariate analyses. In the multiple regression model, patients with higher baseline PINP concentration had a significantly greater LS BMD absolute increase. Prior bisphosphonate use lost its correlation in the multiple regression models. CONCLUSIONS Our results showed that baseline PINP concentration was a useful predictor of LS BMD absolute increase regardless of prior treatment.