Improved method of detection of testosterone abuse by gas chromatography combustion isotope ratio mass spectrometry analysis of urinary steroids

The current approach to detection of doping with testosterone is based on measuring the testosterone to epitestosterone ratio (T/E) in urine by gas chromatography/mass spectrometry, The median T/E for healthy males who have not used T is about 1.0, In a single urine, a T/E lower than six leads to a negative report even though it does not exclude T administration, A value greater than six indicates possible T administration or a naturally elevated ratio, It has been shown previously that the carbon isotope ratio of urinary T changes after T administration, In this study a potential confirmation method for T abuse was optimized, Gas chromatography/combustion/carbon isotope ratio mass spectrometry (GC/C/IRMS) was used to analyze two T precursors (cholesterol and 5-androsten-3 beta,17 beta-diol) and two T metabolites (5 alpha- and 5 beta-androstane-3 alpha,17 beta-diol) in addition to T itself in each of 25 blind urines collected from eight healthy men before, during or after T administration, The carbon isotope ratios of T and the metabolites were lower after T administration, The relationships among the variables were studied using multivariate analysis and beginning with principal components analysis; cluster analysis revealed that the data are composed of two clusters, and classified the samples obtained after T administration in one cluster and the remainder in the other; discriminant analysis correctly identified T users, The measurement of carbon isotope ratios of urinary androgens is comparable to the T/E > 6 test and continues to show promise for resolving cases where doping with T is suspected.