THE ANABOLIC EFFECTS OF HUMAN PARATHYROID-HORMONE (HPTH) ON RAT VERTEBRAL BODY-MASS ARE ALSO REFLECTED IN THE QUALITY OF BONE, ASSESSED BY BIOMECHANICAL TESTING - A COMPARISON STUDY BETWEEN HPTH-(1-34) AND HPTH-(1-84)

PTH has a proven anabolic effect on bone mass, as has been shown in several animal models and treatment regimens. The aim of this study was to ascertain whether the positive effect on bone mass is also reflected in the quality of bone formed. The study was performed in a rat model using human PTH (hPTH). One hundred and twenty male Wistar rats, divided into 10 groups, were given either hPTH-(1-34) or hPTH-(1-84) in daily sc doses. Dose levels ranged from 0.11-3.00 nmol/100 g BW.day for a period of 30 days. At death all six lumbar vertebrae were obtained from each rat. A combination of methods was applied to these vertebral bodies in order to ascertain the effect of hPTH on vertebral bone volume, density, trabecular structure, and biomechanical competence. The results revealed a dose-dependent increase in total volume, dry weight, ash weight, and trabecular bone volume. Also, a dose-dependent increase in load values could be demonstrated. The increase in bone strength remained significant after normalization for both cross-sectional area and bone mass. This indicates that the increase in bone size and bone mass was not achieved at the expense of the quality of the bone present. When the two treatments were administered at the same molar dose level, no difference between hPTH-(1-34) and hPTH-(1-84) was revealed. On the basis of this study, it is concluded that PTH could prove to be a promising treatment in the management of osteopenic states.