The parathyroid hormone, its fragments and analogues - potent bone-builders for treating osteoporosis

As populations age a rising number of men and women, but especially women d uring the first decade after menopause, become victims of a severe, acceler ated loss of bone with crippling fractures known as osteoporosis. This ofte n results in costly, prolonged hospitalisation and perhaps indirectly, deat h. Osteoporosis in women is caused by the menopausal oestrogen decline, whi ch removes several key restraints on the generation, longevity and activity of bone-resorbing osteoclasts. Although there are many antiresorptive drug s on or coming onto the market (calcitonin, bisphosphonates, oestrogen and SERMS) that can slow or stop further bone loss, there are none that can res tore lost bone mechanical strength by directly stimulating osteoblast activ ity and bone growth. However, there is a family of potent, bone-building pe ptides, namely the 84 amino acid parathyroid hormone (PTH). Its 31 to 38 am ino acid N-terminal fragments are currently in or about to enter clinical t rials. We can predict that these peptides will be effective therapeutics fo r osteoporosis especially when supplemented with bisphosphonates or SERMs t o protect the new bone from osteoclasts. These peptides should also acceler ate the healing of fractures in persons of all ages and restore lost bone m ass and mechanical strength to astronauts following their return to earth a fter long voyages in space.