title: 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.
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.
authors.affiliation: LGC, Newmarket Road, Fordham, Cambridgeshire, CB7 5WW, UK.|Drug Control Centre, Analytical and Environmental Sciences Research Divisions, King's College London, 150 Stamford Street, London, SE1 9NH, UK.
authors.forename: Marjaana
authors.initials: M
authors.lastname: Viljanto
authors.affiliation: LGC, Newmarket Road, Fordham, Cambridgeshire, CB7 5WW, UK.
authors.forename: James
authors.initials: J
authors.lastname: Scarth
authors.affiliation: LGC, Newmarket Road, Fordham, Cambridgeshire, CB7 5WW, UK.
authors.forename: Pamela
authors.initials: P
authors.lastname: Hincks
authors.affiliation: British Horseracing Authority, 75 High Holborn, London, WC1V 6LS, UK.
authors.forename: Lynn
authors.initials: L
authors.lastname: Hillyer
authors.affiliation: Racing NSW, Level 11, 51 Druitt Street, Sydney, NSW, 2000, Australia.
authors.forename: Adam
authors.initials: A
authors.lastname: Cawley
authors.affiliation: Racing NSW, Level 11, 51 Druitt Street, Sydney, NSW, 2000, Australia.
authors.forename: Craig
authors.initials: C
authors.lastname: Suann
authors.affiliation: School of Animal and Veterinary Sciences, Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW, 2678, Australia.
authors.forename: Glenys
authors.initials: G
authors.lastname: Noble
authors.affiliation: Drug Control Centre, Analytical and Environmental Sciences Research Divisions, King's College London, 150 Stamford Street, London, SE1 9NH, UK.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Walker
authors.affiliation: Drug Control Centre, Analytical and Environmental Sciences Research Divisions, King's College London, 150 Stamford Street, London, SE1 9NH, UK.
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Kicman
authors.affiliation: Drug Control Centre, Analytical and Environmental Sciences Research Divisions, King's College London, 150 Stamford Street, London, SE1 9NH, UK.
authors.forename: Mark C
authors.initials: MC
authors.lastname: Parkin
mesh_terms: D000818:Animals; D001826:Body Fluids / Q000737:chemistry*; D002853:Chromatography, Liquid; D003687:Dehydroepiandrosterone / Q000032:analysis* / Q000652:urine; D004300:Doping in Sports / Q000706:statistics & numerical data*; D004845:Epitestosterone / Q000032:analysis* / Q000652:urine; D006736:Horses; D006801:Humans; D011355:Prodrugs; D013256:Steroids / Q000032:analysis* / Q000652:urine; D015813:Substance Abuse Detection; D053719:Tandem Mass Spectrometry / Q000379:methods*; D013739:Testosterone / Q000032:analysis* / Q000652:urine
chemical_list: D011355:Prodrugs; D013256:Steroids; D013739:Testosterone; D003687:Dehydroepiandrosterone; D004845:Epitestosterone
keywords: endogenous steroids; gelding; testosterone:epitestosterone ratio; threshold; urine