Parathyroid hormone related protein (1-36)(University of Pittsburgh)

Osteoporosis affects 1.2 million Australians and, in 2012, fractures due to osteoporosis and osteopenia in Australians aged over 50 years cost $2.75 billion. Even minor minimal trauma fractures are associated with increased morbidity and mortality. Despite increasing therapeutic options for managing osteoporosis, fewer than 20% of patients with a minimal trauma fracture are treated or investigated for osteoporosis, so under-treatment is extremely common. Fracture risk assessment is important for selecting patients who require specific anti-osteoporosis therapy. Post-menopausal osteoporosis is frequently due to an imbalance in bone remodelling, with bone resorption exceeding bone formation. Antiresorptive drugs reduce the number, activity and lifespan of osteoclasts, and include bisphosphonates, oestrogen, selective oestrogen receptor-modulating drugs, strontium ranelate, and the human monoclonal antibody denosumab. Teriparatide is the only anabolic agent currently available that stimulates osteoblast recruitment and activity; its antifracture efficacy for non-vertebral fractures increases with the duration of therapy for up to 2 years when it is associated with persisting increases in bone formation rate at the tissue level. Newer anabolic agents are imminent and include an analogue of parathyroid hormone-related protein, abaloparatide, and a humanised monoclonal antibody to an inhibitor of bone formation, romosozumab. Selection of anti-osteoporosis therapy should be individualised to patients, and the duration of bisphosphonate therapy has been covered in recent guidelines. The benefits of treatment far outweigh any risks associated with long term treatment. General practitioners need to take up the challenge imposed by osteoporosis and become champions of change to close the evidence-treatment gap.

Parathyroid hormone-related protein (PTHrP)(1-36) increases lumbar spine (LS) bone mineral density (BMD), acting as an anabolic agent when injected intermittently, but it has not been directly compared with parathyroid hormone (PTH)(1-34). We performed a 3-month randomized, prospective study in 105 postmenopausal women with low bone density or osteoporosis, comparing daily subcutaneous injections of PTHrP(1-36) to PTH(1-34). Thirty-five women were randomized to each of three groups: PTHrP(1-36) 400 µg/day; PTHrP(1-36) 600 µg/day; and PTH(1-34) 20 µg/day. The primary outcome measures were changes in amino-terminal telopeptides of procollagen 1 (PINP) and carboxy-terminal telopeptides of collagen 1 (CTX). Secondary measures included safety parameters, 1,25(OH)2 vitamin D, and BMD. The increase in bone resorption (CTX) by PTH(1-34) (92%) (p < 0.005) was greater than for PTHrP(1-36) (30%) (p < 0.05). PTH(1-34) also increased bone formation (PINP) (171%) (p < 0.0005) more than either dose of PTHrP(1-36) (46% and 87%). The increase in PINP was earlier (day 15) and greater than the increase in CTX for all three groups. LS BMD increased equivalently in each group (p < 0.05 for all). Total hip (TH) and femoral neck (FN) BMD increased equivalently in each group but were only significant for the two doses of PTHrP(1-36) (p < 0.05) at the TH and for PTHrP(1-36) 400 (p < 0.05) at the FN. PTHrP(1-36) 400 induced mild, transient (day 15) hypercalcemia. PTHrP(1-36) 600 required a dose reduction for hypercalcemia in three subjects. PTH(1-34) was not associated with hypercalcemia. Each peptide induced a marked biphasic increase in 1,25(OH)2D. Adverse events (AE) were similar among the three groups. This study demonstrates that PTHrP(1-36) and PTH(1-34) cause similar increases in LS BMD. PTHrP(1-36) also increased hip BMD. PTH(1-34) induced greater changes in bone turnover than PTHrP(1-36). PTHrP(1-36) was associated with mild transient hypercalcemia. Longer-term studies using lower doses of PTHrP(1-36) are needed to define both the optimal dose and full clinical benefits of PTHrP. © 2013 American Society for Bone and Mineral Research. © 2013 American Society for Bone and Mineral Research.