Comparative effects on bone mineral density of tibolone, transdermal estrogen and oral estrogen/progestogen therapy in postmenopausal women

Abstract

The aim of the study was to assess the comparative effects on bone mineral density (BMD) in routine clinical practice of tibolone and estrogen (given either unopposed or combined with cyclical progestogen) in postmenopausal women who had not previously received estrogen or other menopausal therapy.

BMD was measured in the spine and hip by dual energy X-ray absorptiometry (DEXA) at 12-month intervals over 3 years in 82 consecutive postmenopausal women referred for climacteric therapy. Of these, 35 women received tibolone, 24 transdermal estradiol alone and 12 conjugated equine estrogens together with cyclical progestogen; 11 received no therapy other than calcium.

BMD increased significantly in the spine in those taking tibolone over 3 years (p <0.0001 at 1 year; p < 0.0001 at 2 years; and p = 0.03 at 3 years). In those treated with conjugated equine estrogens and cyclical progestogen, BMD in the spine also increased significantly over the first 2 years (p = 0.03 at 1 year; p = 0.004 at 2 years), but not at 3 years. However, although BMD in the spine also rose over 3 years in the women treated with transdermal estradiol alone, the increase was not statistically significant. No significant change in the BMD of either the spine or the hip was observed in the control group. A significant difference in the increase of BMD in the spine between the different treatment groups was observed at 2 years (p = 0.004) in favor of those taking tibolone or conjugated equine estrogens, compared to women who received transdermal estradiol. The highest proportion of individual responders to therapy after 2 years' treatment was observed in those receiving tibolone or conjugated equine estrogens. There was no significant change in the BMD of the hip over 3 years, irrespective of the therapy taken, although there was a tendency towards a progressive increase in the women on tibolone. Neither the age of the women, their body mass index or pretreatment BMD had a significant effect on changes in bone density.

Since tibolone effected a greater increase in spine BMD than did either conjugated equine estrogen with progestogen or transdermal estradiol alone, it is particularly suitable for older women who often have more advanced osteoporosis and who would not accept a return of cyclical bleeding.

Key Words:

• Bone Density
• Menopause
• Tibolone
• Transdermal Estradiol
• Conjugated Equine Estrogen