Abstract

19-norandrosterone glucuronide (19-NA), main urinary metabolite of 19- nortestosterone, 19-norandrostenedione and 19-norandrostenediol, and minor metabolite of norethisterone , can also be produced, albeit in minute amounts, in males and females. Throughout pregnancy, 19-NA can be detected in urine samples at levels reaching approximately 15 ng/mL2. 19-nortestosterone is present in the intact boar; the consumption of meat-rich meal composed of non-castrated pig offal, although highly improbable, will lead to the excretion of 19-NA at levels exceeding the threshold. Adverse analytical findings are reported when the concentration of 19-NA is greater than 2 ng/mL taking into account the uncertainty of the measure; the threshold, introduced in 1998, is adjusted to the specific gravity of the specimen. Recently, the formation of 19-noretiocholanolone (19-NE) and 19-NA, the latter to a lesser extent, was reported in athlete's samples following incubation. Urine samples in which 19-demethylation activity was noted, were often very concentrated and turbid. This crucial observation, confirmed by two different groups, prompted the revision of the criteria for reporting adverse findings to include verification steps in the few samples showing the criteria of unstable urines. It is not possible to determine the endogenous or exogenous origin of urinary 19- norsteroids metabolites by the ratio of their 5a to 5ß metabolites or by the ratio of the glucuro- and sulfoconjugates. The IRMS analysis may permit that differentiation. However, the reliable analysis of urinary 19-NA in trace amount by GC/C/IRMS was not possible without improving instrumental sensitivity and sample purification. We wish to report here, as a confirmation of the work already published by the Laboratory in Cologne, the results of the routinely applied GC/C/IRMS analysis of urine samples containing 19-NA in amount as low as 2 to 3 ng/mL in relatively low volume of urine sample. The IRMS analysis has been utilised to determine the endogenous origin of 19-NA present in athlete's samples as a result of 19-demethylation, thus confirming the occurrence of that reaction in athlete's urine samples. Einleitung (geändert)