Teriparatide (PTH) is the only bone formation therapy that has been approved for the treatment of postmenopausal osteoporosis in Canada. Osteoporosis is currently diagnosed using a bone mineral density (BMD) scan, which measures the amount of mineral (calcium etc) in bones (the higher the amount of mineral, the lower the fracture risk). Although BMD is linked to bone strength and is used to measure fracture risk, it does not give information on bone structure (called bone geometry) which can also tell us a great deal about fracture risks. Clinical trials have shown that teriparatide increases BMD at the lumbar spine and total hip, while BMD at the forearm may decrease after 20 months of therapy. However, bone biopsies of the pelvis done on people taking teriparatide show improvement of bone geometry (ie bone thickness and increased trabeculae (small interconnecting rods of bone), suggesting that a change in bone geometry at the wrist may be occurring as well. Currently, there is a new technology, high resolution pQCT (HR-pQCT) that can assess bone geometry without a biopsy. Since bone strength is affected both by BMD and bone structure (as well as other material properties), our group is interested in examining changes in bone geometry at the radius and tibia in men and women with osteoporosis who receives 24 months of teriparatide therapy. The investigators believe that this new approach of measuring bone strength will help us better understand the mechanisms of therapeutic efficacy of teriparatide. In addition, measuring indices of bone strength such as the material composition (bone mineral content or BMD) and structural properties of bone (size and shape, and microarchitecture) may provide more data about the mechanisms of how teriparatide treatment can decrease fracture risk. In the end, this data will benefit and improve patient care by allowing us to show patients and their providers that whether BMD increases, decreases or stay the same, there are changes in their bone geometric structure with teriparatide therapy that increases bone strength.
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Change in cortical thickness at the radius and tibia as measured by high-resolution quantitative computer tomography (HR-pQCT)
Timeframe: 0-24 months