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Effect of PTH, teriparatide and zoledronic acid on bone microarchitecture


In this open label, non-randomized clinical trial, Hansen et al. employed high resolution peripheral quantitative computer tomography (HR-pQCT) to investigate the impact of osteoporosis treatments on the peripheral skeleton of postmenopausal women with osteoporosis.

Measurements were made on women receiving parathyroid hormone (PTH 1-84 – the full 84 amino acid molecule; 100 μg injected subcutaneously [sc.], daily for 18 months), teriparatide (PTH fragment 1-34 [TPT]; 20 μg sc. Daily for 18 months) and zoledronic acid (ZOL; 5 mg infusion annually).

Cortical porosity increased with TPT and PTH therapy at both the radius (TPT 32±37%, PTH 39±32%; both P<0.001) and the tibia (TPT 13±27%, PTH 15±22%; both P<0.001). TPT also led to moderate increases in cortical thickness at both sites. ZOL did not affect cortical porosity but did increase cortical thickness and cortical density at the tibia, and trabecular volume fraction at both sites.

TPT and ZOL preserved bone strength at both sites, but did not increase it. PTH therapy led to a decrease in bone strength; a drop of 2.8±5.8% (P<0.05) was observed at the radius and a drop of 3.9±4.8% (P<0.001) occurred at the tibia.

Editor’s comment: Although the study design does not allow direct comparison between TPT/PTH and ZOL, the differences observed between these drugs in terms of their effects on cortical bone are not surprising. However, an increase of cortical porosity with TPT/PTH from 2% to 30–40% at the radius seems a lot: is it really all cortical porosity? Even more surprising may be the difference between TPT and PTH, since the latter led to an apparent decrease of estimated strength in the peripheral skeleton.

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