An Experimental Study about the Effects of Parathyroid Hormone on Strength of Vertebra and Bone Density of Proximal Tibia in Ovariectomized Rats / 대한정형외과학회잡지

ABSTRACT

Parathyroid hormone (PTH) has not been studied as extensively as therapeutic agents of osteoporosis, but the anabolic effect of parathyroid hormone on the skeleton has been demonstrated in several studies. The current study was undertaken to assess the effect of parathyroid hormone on bone mass and its biomechanical competence using ovariectomized rat model. Fifty female Sprague Dawley rats of 3 months old were randomized into five groups, 10 in number for each groups. Group I sham-operation, Group II ovariectomy (OVX) plus saline injection, Group III OVX plus PTH 20ug/kg, Group IV OVX plus PTH 40ug/kg, Group V OVX plus PTH 80ug/kg. Treatment regimens were initiated 8 weeks after ovariectomy and continued for 4 weeks thereafter. Bone mineral density was measured in proximal one-third level of tibia by dual energy X-ray absorptiometry (QDR-2000, Hologic, U.S.A). Biomechanical competence was assessed in lumbar vertebral body by universal testing machine (Instron-4467, U.S.A). The average of bone mineral density in sham operated group was 0.088+/-0.0084g/cm (2), and in control group (OVX +/- saline)was 0.065+/-0.0095g/cm (2). Bone mineral density decreased in control group significantly. The average of bone mineral densities in Group III, IV, V (OVX + PTH) were 0.071+/- 0.0089, 0.081+/-0.0086 and 0.084+/-0.0093g/cm (2), respectively. This showed that parathyroid hormone injected groups had significantly higher bone mass than control group (p<0.0#5), and the increment was in proportion to the amount of parathyroid hormone in the range (p<0.05). The average of biomechanical competence of lumbar vertebral body in sham operated group was 30.036.24 MPa and was 25.11+/-5.69 MPa in control group. In Group III, IV,V they were 25.74+/-6.77, 27.96+/-5.17 and 29.83+/-5.79 MPa, respectively. Above results seem supportive of the phenomenon that parathyroid hormone exert anabolic effect on osteoporotic bones in certain experimental condition.