The authors have no conflict of interest
Continuous Parathyroid Hormone Induces Cortical Porosity in the Rat: Effects on Bone Turnover and Mechanical Properties†
Article first published online: 12 APR 2004
Copyright © 2004 ASBMR
Journal of Bone and Mineral Research
Volume 19, Issue 7, pages 1165–1171, July 2004
How to Cite
Lotinun, S., Evans, G. L., Bronk, J. T., Bolander, M. E., Wronski, T. J., Ritman, E. L. and Turner, R. T. (2004), Continuous Parathyroid Hormone Induces Cortical Porosity in the Rat: Effects on Bone Turnover and Mechanical Properties. J Bone Miner Res, 19: 1165–1171. doi: 10.1359/JBMR.040404
- Issue published online: 2 DEC 2009
- Article first published online: 12 APR 2004
- Manuscript Accepted: 24 MAR 2004
- Manuscript Revised: 17 FEB 2004
- Manuscript Received: 21 OCT 2003
- cortical bone;
- torsion testing
We examined the time course effects of continuous PTH on cortical bone and mechanical properties. PTH increased cortical bone turnover and induced intracortical porosity with no deleterious effect on bone strength. Withdrawal of PTH increased maximum torque to failure and stiffness with no change in energy absorbed.
Introduction: The skeletal response of cortical bone to parathyroid hormone (PTH) is complex and species dependent. Intermittent administration of PTH to rats increases periosteal and endocortical bone formation but has no known effects on intracortical bone turnover. The effects of continuous PTH on cortical bone are not clearly established.
Materials and Methods: Eighty-four 6-month-old female Sprague-Dawley rats were divided into three control, six PTH, and two PTH withdrawal (WD) groups. They were subcutaneously implanted with osmotic pumps loaded with vehicle or 40 μg/kg BW/day human PTH(1-34) for 1, 3, 5, 7, 14, and 28 days. After 7 days, PTH was withdrawn from two groups of animals for 7 (7d-PTH/7d-WD) and 21 days (7d-PTH/21d-WD). Histomorphometry was performed on periosteal and endocortical surfaces of the tibial diaphysis in all groups. μCT of tibias and mechanical testing by torsion of femora were performed on 28d-PTH and 7d-PTH/21d-WD animals.
Results and Conclusions: Continuous PTH increased periosteal and endocortical bone formation, endocortical osteoclast perimeter, and cortical porosity in a time-dependent manner, but did not change the mechanical properties of the femur, possibly because of addition of new bone onto periosteal and endocortical surfaces. Additionally, withdrawal of PTH restored normal cortical porosity and increased maximum torque to failure and stiffness. We conclude that continuous administration of PTH increased cortical porosity in rats without having a detrimental effect on bone mechanical properties.