Validation of a GC- and LC-MS/MS based method for the quantification of 22 estrogens and its application to human plasma

In epidemiological studies, blood levels of 17β-estradiol (E2) are associated with hormone-dependent diseases. The lack of specific methods impedes studies on the role of E2 metabolites and their conjugates in the etiology of hormone-dependent diseases. Stable-isotope dilution tandem mass spectrometry methods (coupled to gas chromatography and liquid chromatography systems) for the analysis of 22 endogenous estrogens, including both oxidative metabolites, as well as sulfates and glucuronides, was validated and the method applied to plasma of women with no breast cancer. No changes in estrogen profile during sample cleanup were observed and values for limit of detection (7fmol/ml - 2 pmol/ml), accuracies (80-122%) as well as intra- and inter-day precision (below 28%) at levels near the limit of quantification were acceptable. In human plasma only seven estrogens were detected and estrone conjugates contributed most to the estrogen profile.