Teriparatide: effects on cortical bone microstructure
J. Stepan1, H. Dobnig2, A. Fahrleitner-Pammer2, Y. Ma3, Q. Zeng3, X. Wan3, F. Marin4 & I. Pavo4
Teriparatide (TPTD) reduces the vertebral and nonvertebral fracture risk. TPTD increases bone formation and improves the cancellous bone microstructure which is an important determinant of the mechanical integrity of vertebrae. The aim of our study was to evaluate first time the effect of TPTD on cortical microstructure and dynamic histomorphometric indices in patients with osteoporosis with or without prior therapy with ALN. Sixty-six postmenopausal women with osteoporosis, mean age (S.D.) of 68.0 (7.0) years and mean BMD T-score of −1.7 (0.9) at total hip and −2.8 (0.8) at lumbar spine; 62% with prevalent fractures, have been treated with 20 μg/day subcutaneous TPTD for 24 months; 28 were osteoporosis pretreatment naive (TN), 38 stopped previous ALN treatment (70 mg/week, mean duration of 63.6 months) and switched to TPTD. 45 paired iliac crest biopsies were collected and analyzed for three-dimensional structural changes by micro-computer tomography and for two dimensional structural and dynamic changes by histomorphometry at baseline and after 24-month. At baseline, mineralizing surface/bone surface (MS/BS, %) values were lower in the ALN pretreated group than in the TN, at both the periosteal (0.61±1.29 vs 1.39±0.96; P=0.04) and endocortical surfaces (baseline: 3.16±5.05 vs 6.19±5.07; P=0.06). After 24 months TPTD treatment, the MS/BS (%) increased in the ALN and the TN patients at the periosteal surfaces (1.34±1.05 vs 3.94±2.7; P<0.0001), and endocortical surfaces (4.95±4.03 vs 11±9.57; P=0.005). The cortical porosity was not different between the two groups of patients indicating that alendronate treatment does not reduce cortical porosity. After 24 months TPTD treatment, a significant increase was observed in cortical area and thickness and in double tetracycline labeling of cortical osteons. In summary, TPTD therapy increased bone formation and improved the cancellous and cortical bone quality in postmenopausal women with osteoporosis irrespective of whether they had received prior ALN antiresorptive therapy.
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
Funding: This work was supported, however, funding details unavailable.