Increased loss of trabecular but not cortical bone density, 1 year after discontinuation of 2 years hormone replacement therapy with Tibolone

OBJECTIVE: Assessment of loss of bone density (BD) 1 year after a 2-year period of hormone replacement therapy (HRT) with two doses of Tibolone as compared to placebo in early post-menopausal women.

METHODS: Sixty-four out of 84 women (1-3 years following spontaneous menopause) who completed a 2-year randomised, placebo controlled study to evaluate effects of Tibolone participated in this follow-up study. Quantitative computed tomography was used to exclusively measure trabecular BD, microdensitometry of the mid-phalangeal shaft was used for estimation of cortical BD and biochemical markers of bone metabolism were assessed, 1 year after discontinuation of Tibolone. The study group received either placebo (n = 16), 1.25 mg/day Tibolone (n = 25) or 2.5 mg/day Tibolone (n = 23).

RESULTS: Observations revealed a significantly greater decrease in trabecular BD during the post-trial year in both treatment groups compared to the placebo group (for 1.25 mg/day Tibolone, -6.0%, 95% CI -8.4 to -3.5; for 2.5 mg/day Tibolone, -10.0%, 95% CI: -12.9 to -6.9). In contrast, there was no significant difference in loss of phalangeal BD in both treatment groups compared to placebo. Biochemical markers (serum alkaline phosphatase, urinary excretion of hydroxyproline and calcium) do not suggest an increased bone turnover comparing Tibolone groups to placebo, 1 year after cessation of Tibolone.

CONCLUSION: The present study suggests an increased loss of trabecular but not cortical BD as compared to the placebo group in the first year after cessation of HRT with Tibolone in early post-menopausal women.