Background: We conducted a 5-year prospective, observational, controlled study to assess the effects of tibolone 1.25 mg/day on bone mineral density (BMD) in postmenopausal women with osteopenia or osteoporosis.
Methods: The subjects were 420 women, an average of 66.4 years old, who had been postmenopausal between 8 and 19 years when enrolled in the study. Of the 420 women enrolled, 346 agreed to take tibolone for 5 years. The 74 who refused tibolone took only calcium/vitamin D supplements and served as the control group. BMD was measured in the lumbar spine and total hip region at baseline and annually by dual-energy X-ray absorptiometry (DXA).
Results: At the first two follow-up visits, women taking tibolone had a significant increase in BMD at the spine (P < 0.001) and at the hip (P < 0.001) when compared to baseline values and when compared to BMD values for the control group, which decreased from baseline. In the final 3 years of the study, BMD values (spine and hip) continued to decrease in the control group and also tended to decrease in the tibolone group, but at the end of the fifth year, mean BMD in the tibolone group was still higher than BMD before the start of tibolone treatment (P < 0.05). Calculations showed that if women taking tibolone continued to lose BMD at the same rate as during the final 3 years of the study, after 11 years of tibolone treatment the average patient would have the same BMD as she had when treatment started.
Conclusion: This 5-year observational study provides evidence that tibolone is effective in increasing BMD in postmenopausal women with osteopenia and osteoporosis during the first 2 years of treatment, but because BMD starts to decline in the third year, it is vital that postmenopausal women start treatment with tibolone as early as possible, so that bone mineral density levels are kept high as long as possible.