Application of testosterone to epitestosterone ratio to horse urine – a complementary approach to detect the administrations of testosterone and its pro‐drugs in Thoroughbred geldings. Issue 9 (11th November 2016)

• Record Type: Journal Article
• Authors: Viljanto, Marjaana; Scarth, James; Hincks, Pamela; Hillyer, Lynn; Cawley, Adam; Suann, Craig; Noble, Glenys; Walker, Christopher J.; Kicman, Andrew T.; Parkin, Mark C.
• Other Names: Cawley Adam guestEditor.
• Is Part Of: Drug testing and analysis. Volume 9:Issue 9(2017)
• Page Start: 1328
• Page End: 1336
• Publication Date: 2016-11-11
• Subjects: endogenous steroids -- testosterone:epitestosterone ratio -- gelding -- urine -- threshold; Drugs -- Analysis -- Periodicals; Drug testing -- Periodicals; Chemistry, Forensic -- Periodicals; 615.1901
• DOI: 10.1002/dta.2109
• Languages: English
• ISSNs: 1942-7603

Abstract

Abstract : Detection of testosterone and/or its pro‐drugs in the gelding is currently regulated by the application of an international threshold for urinary testosterone of 20 ng/mL. The use of steroid ratios may provide a useful supplementary approach to aid in differentiating between the administration of these steroids and unusual physiological conditions that may result in atypically high testosterone concentrations. In the current study, an ultra‐high performance liquid chromatography tandem mass spectrometry (UHPLC‐MS/MS) method was developed to quantify testosterone (T) and epitestosterone (E). The method was used to analyze 200 post‐race urine samples from geldings in order to generate the ratios for the reference population. Following statistical analysis of the data, an upper limit of 5 for T:E ratio in geldings is proposed. Samples collected from 15 geldings with atypical urinary testosterone concentrations (>15 ng/mL) but otherwise normal steroid profile, had T:E ratios within those observed for the reference population. The applicability of an upper T:E ratio to detect an administration was demonstrated by the analysis of a selection of incurred samples from testosterone propionate, dehydroepiandrosterone (DHEA), and a mixture of DHEA and pregnenolone (Equi‐Bolic®) administrations. These produced testosterone concentrations above the threshold of 20 ng/mL, but also T:E ratios above the proposed limit of 5. In conclusion, consideration of the T:E ratio appears to be a valuable complementary aid to evaluate whether an atypical testosterone concentration could be caused by a natural biological outlier as opposed to the administration of these steroids. Copyright © 2016 John Wiley & Sons, Ltd. Abstract : The use of steroid ratios may provide a supplementary approach to aid in differentiating the administration of testosterone and its pro‐drugs and unusual conditions resulting in elevated testosterone concentrations in geldings. In the current study, an upper limit of 5 was proposed for the ratio of urinary testosterone: epitestosterone (T:E). Analysis of atypical urine samples showed that the T:E ratio remained below the proposed limit, whilst it was exceeded following the administration of a range of separate testosterone‐related steroids.