Q: MMA fighter Chael Sonnen failed two anti-doping tests which revealed that he used exogenous testosterone. At his recent hearing, his defense was that he was on testosterone replacement therapy (TRT). My question is, how would TRT effect the T/E ratio? Does exogenous testosterone also shutdown epitestosterone production creating a scenario where someone can have a high ratio due to exogenous test, and suppressed epitestosterone production, while sill having “normal” testosterone levels?
A: Chael Sonnen failed the testosterone:epitestosterone ratio (T/E) and the carbon isotope ratio (CIR). The T/E and isotopic tests are two completely different tests.
If a high percentage of an individual’s testosterone is from injection, the isotope test will be failed because the steroid molecules are detectable as being ultimately of plant origin rather than animal origin.
(Synthetic steroids use diosgenin, extracted from the wild yam, as the starting material. Plants incorporate carbon isotopes into the steroid skeleton in a slightly different ratio than animals do.)
But also if a high percentage of an individual’s testosterone is from injection, the T/E ratio will be failed, because when testosterone is produced in the body epitestosterone comes along with it, whereas injected testosterone doesn’t include epitestosterone. If the ratio is too high, it is unlikely or impossible that that much T could have been produced by the body with that little epi-T.
Even if the amount of T is completely reasonable and well within the normal range, or even potentially if low-normal.
If testosterone replacement therapy is allowed it doesn’t make sense to fail athletes for the inevitable outcomes of testosterone replacement therapy (different isotope ratio, increased T/E ratio.)