10">This commentary addresses the discrepancy between changes in areal bone mineral density (BMD) and bone turnover markers (BTM) in concurrent therapy studies leading to possible misinterpretations of the results. In studies of concurrent therapies increases in BMD are generally accompanied by decreases in biochemical markers of bone turnover. This includes Procollagen Type I N-Terminal Propetide (PINP), which has emerged as a reliable marker of bone formation during osteoanabolic therapy. We therefore want to submit, that the larger increases in BMD seen initially in patients on concurrent therapy mask the potential for later reduced osteoanabolic action of PTH. This notion is corroborated by: 1) the lesser impairment of bone anabolism seen with milder antiresorptive modalities like hormone replacement therapy (HRT) or Selective Estrogen Receptor Modulators (SERMs); 2) the changes in BMD seen in extension studies where treatment naïve patients previously treated with PTH alone are crossed over to antiresorptive drugs.
15">We therefore advise against a general use of concurrent therapy with PTH and antiresorptive agents, as it entails blunting of osteoanabolic action of PTH in the long run.