Parathyroid hormone treatment for osteoporosis

There has recently been a dramatic expansion of clinical investigation of parathyroid hormone (PTH). There are no other anabolic agents on the horizon at the current time but clearly there are a large number of questions that remain about this powerful agent for osteoporosis.

The present study reviews clinical trials using PTH alone and in combination and sequence with antiresorptive agents in postmenopausal women and briefly overviews trials in glucocorticoid-induced osteoporosis in men. PTH will be referred to as teriparatide when it is the recombinant human PTH(1-34) fragment produced by Lilly (Indianapolis, Indiana, USA) or the human PTH(1-34) produced by biochemical synthetic methods (Bachem, California, USA); and PTH(1-84) as the intact human recombinant molecule developed by NPS Pharmaceuticals (Salt Lake City, Utah, USA). PTH without other designation denotes either of the compounds.

Because PTH improves microarchitecture, macroarchitecture and mass of bone, it might produce better long-term protection against fracture, when given first and followed by antiresorptive therapy, compared with antiresorptive agents alone. Results of studies on combination therapy must distinguish previously untreated vs. previously treated individuals. PTH should be considered in women with persistent osteoporosis on established bisphosphonates or raloxifene, in which adding PTH might produce better results than switching to PTH. There are still many unanswered questions concerning PTH therapy, one of the most important being the optimal regimen.