Case Study: Atypical δ¹³ C values of urinary norandrosterone

Isotope ratio mass spectrometry (IRMS) has been established in doping control analysis to identify the endogenous or exogenous origin of a variety of steroidal analytes including the 19-norsteroid metabolite norandrosterone (NorA). NorA can be found naturally in human urine in trace amounts due to endogenous demethylation or in situ microbial degradation. The administration of nortestosterone (nandrolone) or different prohormones results in the excretion of urinary NorA. Usually, this can be detected by IRMS due to differing δ¹³ C values of synthetic 19-norsteroids compared to endogenous reference compounds. The consumption of uncastrated pig edible parts like offal or even meat may also lead to a urinary excretion of NorA. In order to determine the δ¹³ C values of such a scenario, urine samples collected after consumption of a wild-boar-testicle meal were analyzed. IRMS revealed highly enriched δ¹³ C values for urinary NorA, which could be related to the completely corn-based nutrition of the animal. Isotopic analysis of the boar's bristles demonstrated a dietary change from C₃ -based forage, probably in winter and spring, to a C₄ -based diet in the last weeks to months prior to death. These results supported the interpretation of an atypical test result of a Central European athlete's doping control sample with δ¹³ C values for NorA of -18 ‰, most probably caused by the consumption of a wild boar ragout. As stated before, athletes should be fully aware of the risk that consumption of wild boar may result in atypical or even adverse analytical findings in sports drug testing.