With this background, we have designed the Treatment of Osteogenesis Imperfecta with Parathyroid Hormone and Zoledronic Acid (TOPaZ) trial to determine if the bone anabolic medicine teriparatide, followed by the bisphosphonate zoledronic acid to maintain increases in BMD that might occur, would be beneficial in reducing the risk of clinical fractures in adults with OI. The gene discussed is PTH; the disease is osteogenesis imperfecta.