title: Carbon isotope ratio mass spectrometry for detection of endogenous steroid use: a testing strategy.
abstract: Isotope ratio mass spectrometry (IRMS) testing is performed to determine if an atypical steroid profile is due to administration of an endogenous steroid. Androsterone (Andro) and etiocholanolone (Etio), and/or the androstanediols (5α- and 5β-androstane-3α,17β-diol) are typically analyzed by IRMS to determine the (13) C/(12) C ratio. The ratios of these target compounds are compared to the (13) C/(12) C ratio of an endogenous reference compound (ERC) such as 5β-pregnane-3α,20α-diol (Pdiol). Concentrations of Andro and Etio are high so (13) C/(12) C ratios can easily be measured in most urine samples. Despite the potentially improved sensitivity of the androstanediols for detecting the use of some testosterone formulations, additional processing steps are often required that increase labour costs and turnaround times. Since this can be problematic when performing large numbers of IRMS measurements, we established thresholds for Andro and Etio that can be used to determine the need for additional androstanediol testing. Using these criteria, 105 out of 2639 urine samples exceeded the Andro and/or Etio thresholds, with 52 of these samples being positive based on Andro and Etio IRMS testing alone. The remaining 53 urine samples had androstanediol IRMS testing performed and 3 samples were positive based on the androstanediol results. A similar strategy was used to establish a threshold for Pdiol to identify athletes with relatively (13) C-depleted values so that an alternative ERC can be used to confirm or establish a true endogenous reference value. Adoption of a similar strategy by other laboratories can significantly reduce IRMS sample processing and analysis times, thereby increasing testing capacity.
authors.affiliation: UCLA Olympic Analytical Laboratory, Department of Pathology & Laboratory Medicine, Geffen School of Medicine, Reagan UCLA Medical Center, Los Angeles, CA 90095-7418, USA. abutch@mednet.ucla.edu
authors.forename: Brian D
authors.initials: BD
authors.lastname: Ahrens
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Butch
mesh_terms: D000738:Androsterone / Q000652:urine; D056352:Athletes; D002247:Carbon Isotopes; D004300:Doping in Sports; D005043:Etiocholanolone / Q000652:urine; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods* / Q000592:standards; D013256:Steroids / Q000652:urine*; D015813:Substance Abuse Detection / Q000379:methods* / Q000592:standards
chemical_list: D002247:Carbon Isotopes; D013256:Steroids; D005043:Etiocholanolone; D000738:Androsterone
keywords: carbon isotope ratio; doping control; endogenous steroids; isotope ratio mass spectrometry; testosterone