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Tibolone is not aromatized in postmenopausal women

Tibolone is not aromatized in postmenopausal women In the article of Kuhl and Wiegratz entitled ‘Can 19-nortestosterone derivatives be aromatized in the liver of adult humans? Are there clinical implications?’, the authors made the statement that the producer of tibolone was withholding clinical data about the aromatization of tibolone to 7a-methyl-ethinylestradiol (7a-MEE). This is not correct, because the results of the study were submitted to Menopause in June 2006, accepted in September 2006 and published in 2007. It often takes time for the results of a study, in which new and well-validated methods are used, to become available and to be finally published. The conclusion of the study is: ‘7a-MEE is not a metabolite of tibolone but it is a chemical artifact generated during analytical procedures with derivatization. Using liquid chromatography-mass spectrometry (LC-MS/MS) without derivatization, 7a-MEE cannot be demonstrated in plasma from postmenopausal women after single and multiple doses of tibolone.’ Kuhl and Wiegratz could not be aware of this study in the public domain. In their article, Kuhl and Wiegratz also discussed the effects of tibolone on the endometrium, but they did not mention the outcome of THEBES (Tibolone Histology of the Endometrium and Breast Endpoints Study) in their evaluation. The results of this large, randomized, double-blind study were available when the revised manuscript of Kuhl and Wiegratz was submitted to Climacteric. The conclusions of the study were that the THEBES results confirm previous findings that tibolone does not induce endometrial hyperplasia or carcinoma in postmenopausal women, and it is associated with a better vaginal bleeding profile than conjugated equine estrogens/medroxyprogesterone acetate.