Does tibolone exacerbate atherosclerosis?

Tibolone is widely used in many countries (though not in theUSA) for the treatment of post-menopausal symptoms and to inhibitpost-menopausal bone loss. Tibolone's popularity likely reflectsthe observation that it equals traditional hormone therapy inthe relief of hot flushes, vaginal dryness, and the preventionof bone loss and, in addition, appears to increase libido. Thepost-menopausal benefits of tibolone relate to the uniquenessof the metabolism of the parent molecule. In human and non-humanprimates, tibolone is converted to three metabolites. Two areweak estrogen agonists (the 3-alpha and 3-beta hydroxy metabolites).The third metabolite, the delta-4 isomer, is a molecule thatbinds both to the progesterone receptor and to the androgenreceptor with progestogenic and androgenic effects. Although tibolone has numerous benefits for post-menopausalwomen, it markedly lowers plasma concentrations of the HDL withconsistent reductions of