Background and Objective: Although there are several methods of treatment of osteoporosis, prospective studies to compare their effect on bone density in Iranian population are rare. This study was designed to compare the effect of alendronate and hormone replacement therapy on bone mineral density of postmenopausal Iranian women living in Zanjan.

 Materials and Methods: We treated 115 women (mean age 54/8±9 years). Twenty four women were treated with conjugated equine estrogen (0.625 mg), 5 mg medroxyprogesterone, and 1000 mg elemental calcium with 400 IU vitamin D daily. Forty four subjects received 10 mg/d alendronate plus calcium and vitamin D in the same dose and 37 women were taken placebo with 1000 mg/d calcium and 400 IU/d vitamin D. Their bone mineral densities (BMD) were measured at the lumbar spine, hip and mid radius every 12 months for three years. All cases with secondary osteoporosis were excluded from the study.

Results: Significantly a higher percentage increases in BMD at the lumbar spine (P< .008, 2-way analysis of variance) were found in the alendronate group than in the HRT and calcium + vitamin D groups throughout the 36-month study period. However, there was no difference in BMD at the femoral neck and mid-radius between alendronate and HRT groups. Treatment with alendronate resulted in a 11% increase at the L-spine BMD (P: 0/00). A non significant reduction of about 4% at the femoral neck BMD was detected in alendronate group at the end of the 3-year study period. Although there was no significant change in the femoral neck, lumbar spine or mid-radius BMD with HRT, a significant decline (about 9%) in the BMD of the femoral neck was observed in the placebo group (P: 0.004). There was no difference in upper gastrointestinal or drug-related side effects between the groups.

 Conclusion: Our data suggest that the use of alendronate was well tolerated for 3 years and significantly increased BMD at the L-spine. It also can reduce the rate of BMD reduction at the femoral neck as was seen in the placebo group in postmenopausal Iranian women. Although HRT can inhibit BMD reduction at the femoral neck and lumbar spine, this regimen can not increase BMD in postmenopausal Iranian women.