Aging is characterized by an age-dependent reduction in bone density. Pronounced bone loss by postmenopausal estrogen deficiency induces a bad effect on dynamic balance of bone metabolism . When the bone density is reduced to the level below the
fracture threshold, the risk for fracture is greatly increased. Osteoporosis-induced fractures as a result, especially around hip joint, inevitably need the operative treatment.
Thus, in order to decrease the occurrence of new fractures, a corrective therapy is needed to stimulated bone formation, Antiresorptive agents such as estrogen and calcitonin inhibit bone resorption at early period of menopause, but are not
effective
for established osteoporosis.
However, parathyroid hormone is approved as an effective agent available for the treatment of osteoporosis such as an anabolic effect on bone density and a positive effect on the rate of osteoporosis-induced fractures.
The aim of present study is to elucidate the effects of estrogen, calcitonin, parathyroid hormone alone or combination therapy of parathyroid hormone with estrogen or calcitonin on the strength of the femur neck and the amount of bone mineral
density of
the proximal tibia in ovariectomized rats.
Sixty-four female rats (Sprague-Dawley rat), of three months old and weighing in 250gm~300gm, were used for the experiment. Fifty-five rats were ovariectomized and divided into six groups and remaining nine rats were subjected to sham-operation.
All
groups were untreated for eight weeks to induce significant bone loss. Then they were administrated of hormone for four weeks according to protocols except control and sham-operation group.
They consisted of group I(n=10) for control, group II (n=9) for sham-operation, group III (n=9) for administration of estrogen, group IV (n=10) for parathyroid hormone, group V (n=8) for calcitonin, group VI (n=9) for parathyroid hormone with
calcitonin and group VII (n=9) for parathyroid hormone with estrogen.
The retrieved femurs were harvested to biomechanical testing using universal testing machine (Instron-4467) and ipsilateral proximal tibias were assessed for bone mineral density with dual energy x-ray absorptiometry (Hologic QDR 2000). These
results
were statistically analyzed by unpaired student t-test.
@ES The results obtained were as follows :
@EN 1. The mean mechanical strength of femur neck was 182.98±33.25 MPa in control group (group I), 220.53 ±34.61 MPa in Group II, 233.90 ±56.64 MPa in group III, 217.08 ±17.73 MP3 in group IV and 190.61 ±43.74 MPa in group V, 198.84 ±26.29
MPa in
group VI and 213.80 ±19.88 MPa in group VII. As compar5ed with the result of control group, the results of group II, III, IV, VII were statistically significant (P<0.05), however, of group V and VI were statistically insignificant (P>0.05).
2. The mean bone mineral density of the proximal tibia were 0.006 ±0.0095 gm/㎤ in control group (group I), 0.008 ±0.0084 gm/㎤ in group II, 0.081 ±0.0094 gm/㎤ in group III, 0.085 ±0.0093 gm/㎤ in group IV and 0.069 ±0.0112 gm/㎤ in group
V,
0.079 ±0.0111gm/㎤ in group VI and 0.079 ±0.0117 gm/㎤ in group VIII. As compared with the result of control group, the results of group II, III, IV, VI, VII was statistically significant (P<0.05), however, of group V was insignificant
(P>0.05).
Thus, these findings provide a support for using estrogen or parathyroid hormone in the treatment of postmenopausal osteoporosis. The combination treatment of the parathyroid hormone with estrogen or calcitonin is shown no outstanding advantage
over the
treatment with estrogen or parathyroid hormone alone. The treatment of calcitonin does not promise any potential of its use in the postmenopausal osteoporosis.
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