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Tibolone and its effects on bone: a review.
B Berning1, H J Bennink, B C Fauser
1Department of Obstetrics and Gynecology, Leyenburg Hospital, The Hague.
Summary
Tibolone, a synthetic steroid, effectively prevents bone loss and increases bone density in both rats and postmenopausal women. Its bone-protective effects are mediated through estrogen receptors, similar to estrogen therapy.
Area of Science:
- Endocrinology
- Pharmacology
- Bone Biology
Background:
- Tibolone is a synthetic steroid with a unique mixed hormonal profile (estrogenic, progestogenic, androgenic).
- Its mechanism of action involves complex receptor-mediated and metabolic pathways at the tissue level.
Purpose of the Study:
- To review the existing evidence on the effects of tibolone on bone health.
- To evaluate tibolone's efficacy in preventing and treating bone loss and osteoporosis.
Main Methods:
- Review of preclinical studies in rats (ovariectomy, low calcium diet models).
- Analysis of clinical trials in early- and late-postmenopausal women.
- Examination of comparative studies with hormone replacement therapy.
Main Results:
- Tibolone prevents bone loss and increases bone mineral density in rats, with effects blocked by antiestrogens.
- Tibolone (2.5 mg/day and 1.25 mg/day) prevents bone loss in postmenopausal women and increases bone density in osteoporotic patients.
- Tibolone demonstrates comparable efficacy to conventional hormone replacement therapy but lacks direct comparisons with bisphosphonates or raloxifene.
Conclusions:
- Tibolone exhibits significant bone-protective effects mediated by estrogen receptors in both animal models and human clinical trials.
- Further studies are needed to confirm tibolone's efficacy in reducing osteoporotic fracture risk.
- Tibolone is effective in preserving bone density in patients undergoing gonadotropin-releasing hormone agonist therapy.