3% increase in hip BMD measured using DXA. These associations were even more striking when BMD changes were measured by quantitative Protein Tyrosine Kinase inhibitor computerized tomography (QCT): thus, each SD increase in the 3-month change in PINP was associated with a 21.2% increase in spine QCT trabecular BMD and a 7.0% increase in hip QCT trabecular BMD. There are several limitations of this study. First, it was open-label and did not include a placebo or control group.

However, biochemical markers of bone turnover and BMD are unlikely to be influenced by a lack of blinding. Moreover, the central laboratory personnel who performed the analyses were blind to the patients’ treatment assignments and previous medication history. Second, because data on prior osteoporosis treatments were obtained retrospectively at baseline, we do not have accurate details on adherence and compliance to those treatments. Third, only bone

formation markers and not bone resorption markers were measured; therefore, we do not get a full picture of bone turnover. Fourth, the number of fractures observed in this cohort was small. Thus, the lack of a significant relationship between changes in biochemical markers and fracture risk should be interpreted with caution. Further studies are needed to define the role of biochemical markers as predictors of fracture risk during teriparatide therapy. Finally, the subjects of this study were not randomized GS-9973 to the three analysis subgroups, which represent observational cohorts. The strength of this study lies in its external validity. We included women with severe postmenopausal osteoporosis regardless of prior antiresorptive treatment and their click here response (or lack of response) to it. By keeping the inclusion and exclusion criteria broad, it was possible to recruit almost all women for whom teriparatide was indicated, thereby assembling a study cohort whose properties are similar to those of patients suitable for treatment with teriparatide in routine care. Of note, we only analyzed patients who had stopped their

prior antiresorptive therapy before many starting teriparatide; therefore, our results may differ from those studies where patients continued the antiresorptive concomitantly with teriparatide [15, 19]. In conclusion, teriparatide treatment is associated with a significant increase in biochemical markers of bone formation at 1 and 6 months. The bone formation marker response in patients does not seem to be adversely influenced by prior antiresorptive therapy, and can be detected at 1 month of therapy. After 6 months of treatment, bone formation markers are at a similar level regardless of prior osteoporosis treatment. Although indices of bone formation or change in formation were only modestly predictive of change in BMD at the spine or total hip at 24 months, and were not correlated with fracture outcomes, PINP appears to be the most sensitive bone marker to assess a therapeutic response to teriparatide.