Testosterone Doping: Dealing with Genetic Differences in Metabolism and Excretion

Abstract

The first documented use of testosterone as a performanceenhancing substance in sport began in the 1950s. The success of Russian weightlifters during this era led Dr. John B. Zeigler to surreptitiously obtain information from their trainers that they were using testosterone. Later, Zeigler would use Dianabol to enhance the performance of weightlifters at the York Barbell Club beginning in 1958. Once Pandora’s Box was open, it was impossible to close. The growth and widespread use of anabolic steroids in many competitive sports eventually led the U.S. Congress to schedule testosterone and other anabolic agents under the Anabolic Steroids Control Act in 1990 (Public Law 101647). For many years, the medical community argued that there was no proof that testosterone enhanced athletic performance. Finally, in 1996, Bhasin and co-workers showed that supraphysiological doses of testosterone indeed produced performance benefits (1), something the athletes had known for four decades. The urinary testosterone to epitestosterone (T/E) ratio was the first test to be used for evaluation of abuse of a natural (or endogenous) substance such as testosterone to enhance performance in sport. The production of reliable quadrupole gas chromatograph/mass spectrometers in the mid-1970s allowed more widespread study of urinary steroid profiles. Donike and coworkers (2) observed an unusual distribution of testosterone concentrations in samples collected at the Moscow Olympics in 1980. In 1982, Donike proposed the use of the urinary T/E ratio based on the observation that epitestosterone was excreted in the urine in a relatively constant amount and as such constituted a way to compensate for the variability in testosterone concentration that occurred as a function of the diluteness of the urine (2). Because the primary metabolite of testosterone is testosterone glucuronide, the procedure developed by Donike used -glucuronidase in the preparation of the samples for analysis. In 1983, the International Olympic Committee accepted a T/E ratio of greater than 6:1 as evidence of testosterone doping, based on the 99th percentile of the log normal distribution of ratio values established by Donike and his co-workers. It was soon clear that the T/E ratio based on population reference ranges had limitations. For example, it had been noted in 1970 that genetic make-up could have a significant effect on urinary testosterone excretion, whereas epitestosterone excretion was unaffected (3). As population T/E ratio data accumulated in the anti-doping laboratories, it was clear that there were two distributions of urinary T/E ratios in both men and women, one with a maximum frequency at a T/E ratio of about 0.1 and a much larger population with a maximum frequency at a T/E ratio of about 1. Within the anti-doping community, the smaller population was referred to as low mode, and it was known that administration of testosterone to low-mode individuals did not result in a T/E ratio above the population threshold (4). Jakobsson and her colleagues (5) provided the mechanism for lowmode excretion in 2006 when they demonstrated that the UGT2B17 gene deletion was the cause of significant differences in testosterone glucuronide excretion between Korean and Swedish men. In their current paper in this issue, JakobssonSchulze et al. (6) report that when subjects deficient in the UGT2B17 gene (del/del) receive exogenous testosterone, their T/E ratio does not rise above the current population-based threshold of 4:1. One potential route of excretion of testosterone in UGT2B17 del/del genotypes is through other phase II metabolites such as testosterone sulfate. Borts and Bowers (7) directly measured the concentrations of testosterone and epitestosterone sulfate and glucuronide using HPLC/tandem mass spectrometry. Low-mode excretors did not produce larger than normal amounts of testosterone or epitestosterone sulfate. There was also no change in the relative production of sulfate conjugates. Because phase II metabolism does not explain the difference in testosterone handling in these individuals, it would be interesting to know what phase I metabolism products are increased in individuals with the UGT2B17 del/del polymorphism. This information may help develop a more sensitive test for testosterone