Systemic bone formation with weekly PTH administration in ovariectomized rats.

Purpose: Weekly subcutaneous adminis- tration of 0 (vehicle), 10 and 80 µg/kg doses of human parathyroid hormone (1-34) (PTH (1-34)) were com- pared based on their capacity to induce systemic for- mation of bone in 9 month-old ovariectomized (OVX) Sprague-Dawley rats. Methods: Changes elicited at bone tissue after 4 weeks of treatment were assessed using dual x-ray absorptiometry, micro-computed tomography (µCT), and ashing. Results: The 10 µg/kg dose led to a significant increase (p<0.025) in femoral bone mineral density (BMD) over vehicle- and 80 µg/ kg-treated groups. Similarly, structural analysis of the femoral neck trabecular bone by µCT revealed increases in bone volume fraction and trabecular thick- ness over the pre-treatment baseline, and vehicle- and 80 µg/kg-treated groups. Conclusions: The data sug- gest that the weekly administration of 10 µg/kg of PTH (1-34) was sufficient to significantly promote the bone mineral density systemically. The weekly admin- istration of 10 µg/kg over a 4-week treatment period is, to our knowledge, one of the lowest reported total dose of PTH (1-34) shown to induce a net anabolic effect on skeletal tissue in OVX rats.