7alpha-Methyl-ethinyl estradiol is not a metabolite of tibolone but a chemical stress artifact

• Published in: Menopause (New York, N.Y.) Vol. 14; no. 3 Pt 1; p. 474
• Main Authors: Dröge, Melloney J, Oostebring, Freddy, Oosting, Ep, Verheul, Herman A M, Kloosterboer, Helenius J
• Format: Journal Article
• Language: English
• Published: United States 01.05.2007
• Subjects: Chromatography, Liquid; Estradiol - analogs & derivatives; Estradiol - chemistry; Estrogen Receptor Modulators - administration & dosage; Estrogen Receptor Modulators - chemistry; Estrogen Receptor Modulators - metabolism; Female; Gas Chromatography-Mass Spectrometry; Humans; Middle Aged; Norpregnenes - administration & dosage; Norpregnenes - chemistry; Norpregnenes - metabolism; Postmenopause; Sensitivity and Specificity
• ISSN: 1072-3714

This study was conducted to establish whether 7alpha-methyl-ethinyl estradiol (7alpha-MEE) in plasma from postmenopausal women treated with tibolone is a metabolite or an artifact. Clinical samples with known levels of tibolone metabolites, plus plasma samples spiked with tibolone and metabolites, were analyzed for levels of 7alpha-MEE using liquid chromatography-mass spectometry (LC-MS/MS) with and without derivatization. Approximately 20 to 40 pg/mL 7alpha-MEE was detected using LC-MS/MS with derivatization in plasma samples from postmenopausal women treated with tibolone. In plasma samples spiked with 200 ng/mL tibolone or Delta-tibolone, LC-MS/MS with derivatization revealed the generation of around 200 and 36 pg/mL 7alpha-MEE, respectively, whereas LC-MS/MS without derivatization showed no detectable chemical conversion of tibolone to 7alpha-MEE. Generation of 7alpha-MEE is increased by the "stress conditions" used in the derivatization procedure; simply drying the sample also shows this artifactual conversion. The major active and sulfated 3-hydroxy metabolites of tibolone are not converted to 7alpha-MEE. Without derivatization, and avoiding stress conditions, no detectable levels (<20 pg/mL) of 7alpha-MEE were found in plasma samples from postmenopausal women treated with single (eight participants at 13 time points) or multiple (seven participants at 18 time points) doses of tibolone. 7alpha-MEE is not a metabolite of tibolone but is a chemical artifact generated during analytical procedures with derivatization. Using LC-MS/MS without derivatization, 7alpha-MEE cannot be demonstrated in plasma from postmenopausal women after single or multiple doses of tibolone.