Peng, S. H, Segura, J., Farre, M., Gonzalez, J. C, de la Torre, X. (2002). Plasma and urinary markers of oral testosterone undecanoate misuse. Steroids, 67, 39-50.

"Orally administered testosterone undecanoate (TU), an anabolic, androgenic steroid, can potentially be abused by athletes. Indirect evidence for detecting oral TU intake could be deduced from the changes in steroid profile post-administration. Direct evidence could be obtained by detection of unchanged TU in plasma. To this end, both urinary and plasma steroid profiles of six healthy male subjects given a single oral dose of 120 mg of TU were studied by gas chromatography/mass spectrometry (GC/MS) and gas chromatography/tandem mass spectrometry (GC/MS/MS). The increased concentration of glucuronidated testosterone in plasma appears to be the most characteristic sign of oral TU intake. The testosterone glucuronide (TG)/nonconjugated testosterone (T) ratio, TG/17-hydroxyprogesterone (17OHP) ratio, and TG/luteinizing hormone (LH) ratio were observed to be significantly elevated above their basal levels for 10 hours, and 6 hours, respectively. Urinary ratios of TG/epitestosterone glucuronide (EG) were found to be higher than the cut-off value of 6 for the period 4 to approximately 8 hours post-administration, but only in three subjects. One subject failed to respond with respect to all of the above-mentioned indirect markers, as TG was not significantly increased in either plasma or urine. Unchanged TU was directly detected in plasma of all six subjects from approximately 1.5 hours to 4 approximately 6 hours after oral TU intake by GC/MS/MS, providing unequivocal proof of exogenous testosterone intake. Distinct and complementary markers for detecting oral TU intake could be obtained from plasma and urine, respectively".

Implication. This shows how differently individuals react to drugs. One of the six Ss in this study showed no reactivity at all. The presence of testosterone undecanoate was observed in all Ss while other markers were exhibited in only three Ss. Consequently, one should not expect drug tests to reveal exogenous introduction of banned substances in a similar manner or across the same period. Such testing might only locate those who react (true-positives) rather than all those who use (which includes false-negative results).

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