delta13C-values of endogenous urinary steroids.

By means of gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) urinary steroids obtained from a reference population of 56 subjects were analyzed for their (13)C/(12)C-ratios. The analytes encompassed androsterone (A), etiocholanolone (E), 11beta-hydroxyetiocholanolone (OHE), 11beta-hydroxyandrosterone (OHA), and 5beta-pregnane- 3alpha,20alpha-diol (PD). A and E represent androgen metabolites (AM). PD, OHE, and OHA have sources independent from androgen metabolism. The delta(13)C-values of the latter compounds may be compared to those of AM in order to detect doping with synthetic androgens and thus may serve as endogenous reference compounds (ERC). In order to allow for classification of conspicuous samples, reference ranges and limits were calculated for delta(13)C-values of selected steroids and differences hereof (Delta(13)C-values). When A is compared to ERCs, Delta(13)C-values larger than 3 per thousand are very unlikely. A set of additional parameters was surveyed by a questionnaire. Several factors turned out to exert significant influence on the delta(13)C-values of urinary steroids. These encompass the identity of the steroid itself, sex, oral contraception, travels, and physical activity.