7&agr;-Methyl-ethinyl estradiol is not a metabolite of tibolone but a chemical stress artifact

  title={7\&agr;-Methyl-ethinyl estradiol is not a metabolite of tibolone but a chemical stress artifact},
  author={Melloney Joyce Dr{\"o}ge and Freddy Oostebring and Ep Oosting and Herman A. M. Verheul and Helenius Jan Kloosterboer},
Objective:This study was conducted to establish whether 7&agr;-methyl-ethinyl estradiol (7&agr;-MEE) in plasma from postmenopausal women treated with tibolone is a metabolite or an artifact. Design:Clinical samples with known levels of tibolone metabolites, plus plasma samples spiked with tibolone and metabolites, were analyzed for levels of 7&agr;-MEE using liquid chromatography-mass spectometry (LC-MS/MS) with and without derivatization. Results:Approximately 20 to 40 pg/mL 7&agr;-MEE was… 
5 Citations
Tibolone is not aromatized in postmenopausal women
  • H. Kloosterboer
  • Medicine
    Climacteric : the journal of the International Menopause Society
  • 2008
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.
[Effect of tibolone on endometrium of castrated rats].
High doses of tibolone, given for long periods of time to castrated female rats, have an estrogenic effect which can be dose-dependent, causing proliferation in the endometrium and causing changes in the cell differentiation (squamous metaplasia), but do not lead to hyperplasia.
Recent advances on the action of estrogens and progestogens in normal and pathological human endometrium
Treatment with hormone replacement therapy (estrogens+progestogens), as well as with tibolone, is most effective in protecting this tissue by climacteric alterations, owing to the significant decrease of ovarian hormones.
The other side of progestins: effects in the brain.
The role exerted by different progestins, currently used for contraception or in postmenopausal hormone replacement therapies, in regulating cognitive functions as well as social behavior and mood is reported.


Conversion of tibolone to 7&agr;-methyl-ethinyl estradiol using gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry: interpretation and clinical implications
The findings prove that conversion of tibolone to MEE is an artifact that is generated in a GC- MS system and is largely due to the intense heating step involved in GC-MS.
Formation of 7&agr;-methyl-ethinyl estradiol during treatment with tibolone
Investigation of whether tibolone, which is orally used for hormone replacement therapy, is transformed to a derivative of ethinyl estradiol (EE), demonstrates that, during daily treatment of women with 2.5 mg tiblone, a small proportion of tIBolone is transformation to 7&agr;-methyl-EE.
Tibolone and its delta-4, 7α-methyl norethisterone metabolite are reversible inhibitors of human aromatase
Inhibition of oestrone sulphatase activity by tibolone and its metabolites.
Results from this study have confirmed that tibolone and its metabolites can inhibit E1-STS activity and may explain the absence of breast stimulation as observed in clinical studies.
Progestagenic Effects of Tibolone on Human Endometrial Cancer Cells
An endometrial carcinoma cell line (Ishikawa PRAB-36) was used to investigate the progestagenic properties of tibolone and its metabolites and it was found that 3β-OH-tibolon also induces some inhibition of growth.
The in vivo human metabolism of tibolone.
Tibolone and its metabolites are not likely to play a clinically significant role at the level of these cytochrome P450 enzymes with regard to the metabolism of coadministered drugs.
Tibolone: a compound with tissue specific inhibitory effects on sulfatase