Genetic Variations in UDP-Glucuronosyl Transferase 2B17: Implications for Testosterone Excretion Profiling and Doping Control Programs

B. Starcevic, A. W. Butch
2008 Clinical Chemistry  
The use of drugs and ergogenic substances to augment athletic performance, commonly referred to as doping, has evolved along with sporting events. Ancient Olympic athletes consumed mushrooms, plants, and herbs in an attempt to gain a competitive edge. The modern Olympic Games made their debut in 1896, and mixtures of cocaine, ephedrine, and strychnine were used to enhance performance. Anabolic androgenic steroids (substances similar to the hormone testosterone) were used after World War II by
more » ... viet athletes to increase muscle mass and power in weightlifting and bodybuilding events. Anabolic androgenic steroids rapidly spread to athletes in other sporting events and are still a problem in today's sports world. To deal with the problem of doping in sports, the International Olympic Committee established a Medical Commission. The first list of prohibited substances was created in 1967; drug testing was implemented at Olympic Games the following year. In 1999, an independent international organization, the World Anti-Doping Agency (WADA), was created to combat doping in sports and provide unified standards for doping control. The T/E Ratio to Screen for Testosterone Use Anabolic androgenic steroids are the most abused class of prohibited substances, with testosterone accounting for many positive cases. Testosterone abuse is problematic because synthetic testosterone is indistinguishable from endogenous testosterone by routine screening methods such as gas chromatography-mass spectrometry. In the 1980s, it was discovered that testosterone use alters the ratio of testosterone glucuro-nide to epitestosterone glucuronide (T/E ratio) 2 in urine. Epitestosterone is a naturally occurring biologically inactive epimer of testosterone that remains relatively constant in urine. A population-based T/E ratio cutoff of 6.0 was initially used to indicate synthetic testosterone use; the T/E ratio cutoff was lowered to 4.0 in 2005. Based on data from several laboratories, the average T/E ratio ranges from 0.9 to 1.6 for healthy male adolescents and men. At the UCLA Olympic Analytical Laboratory, we found that the average T/E ratio during a 31-month period was 1.1 (median 0.9%). The distribution of T/E ratios is shown in Fig. 1 . Approximately 99.6% of urine samples have a T/E ratio Ͻ4.0, and 99.8% have a T/E ratio Ͻ6.0. Confirmation Testing for Testosterone Use The T/E ratio is typically used as a screening test, and urine samples with a ratio Ͼ4.0 are submitted for confirmation testing by gas chromatography/combustion/ isotope ratio mass spectrometry (GC/C/IRMS). GC/C/ IRMS has excellent specificity and can measure very small differences in the 13 C to 12 C ratio of testosterone and steroid metabolites. The 13 C content of natural (endogenously produced) testosterone is influenced by plant and animal sources consumed in food. In contrast, synthetic (pharmaceutical) testosterone is produced from plant precursors (stigmasterol) containing less 13 C. This results in smaller 13 C/ 12 C ratios for synthetic testosterone, compared to natural testosterone. 13 C/ 12 C ratios are expressed in parts per thousand relative to a reference gas as a ␦ notation. The ␦ value is compared to that obtained for a compound in the steroid pathway such as pregnanediol, whose 13 C/ 12 C ratio is unchanged by testosterone use. If the ␦ value for the metabolite differs from the reference compound (pregnanediol) by 3 or more units, synthetic steroid use is indicated. Although GC/C/IRMS is used to confirm testosterone use, the technique has low
doi:10.1373/clinchem.2008.110106 pmid:18927247 fatcat:3aiotldhnzg3hpsszhkb243ori