In the TN and ALN groups, respectively, mean increases in three-dimensional bone volume/tissue volume were 105 % and 55 % , and trabecular thickness 30.4 % and 30.8 %. 12-month changes in biochemical bone markers correlated significantly with improvements in bone volume/tissue volume, trabecular number, and reduction of trabecular separation, for PINP and βCTX, respectively. We conclude that cancellous bone microstructure improved with teriparatide therapy irrespective of prior antiresorptive use.