Effects of daily treatment with parathyroid hormone on bone microarchitecture and turnover in patients with osteoporosis: A paired biopsy study

We examined paired iliac crest bone biopsy specimens from patients with ost eoporosis before and after treatment with daily injections of 400 U of reco mbinant, human parathyroid hormone 1-34 [PTH(1-34)]. Two groups of patients were studied. The first group was comprised of 8 men with an average age 4 9 years. They were treated with PTH for 18 months. The second group was com prised of 8 postmenopausal women with an average age 54 years. They were tr eated with PTH for 36 months. The women had been and were maintained on hor mone replacement therapy for the duration of PTH treatment. Patients were s upplemented to obtain an average daily intake of 1500 mg of elemental calci um and 100 IU of vitamin D. The biopsy specimens were subjected to routine histomorphometric analysis and microcomputed tomography (CT). Cancellous bo ne area was maintained in both groups. Cortical width was maintained in men and significantly increased in women. There was no increase in cortical po rosity. There was a significant increase in the width of bone packets on th e inner aspect of the cortex in both men and women. This was accompanied by a significant decrease in eroded perimeter on this surface in both groups. Micro-CT confirmed the foregoing changes and, in addition, revealed an inc rease in connectivity density, a three dimensional (3D) measure of trabecul ar connectivity in the majority of patients. These findings indicate that d aily PTH treatment exerts anabolic action on cortical bone in patients with osteoporosis and also can improve cancellous bone microarchitecture. The r esults provide a structural basis for the recent demonstration that PTH tre atment reduces the incidence of osteoporosis-related fractures.