Urinary analysis of 16(5α)-androsten-3α-ol by gas chromatography/combustion/isotope ratio mass spectrometry:: implications in anti-doping analysis

We present a method for the analysis of urinary 16(5alpha)-androsten-3alpha-ol together with 5beta-pregnane-3alpha,20alpha-diol and four testosterone metabolites: androsterone (Andro), etiocholanolone (Etio), 5alpha-androstane-3alpha,17beta-diol (5alphaA), 5beta-androstane-3alpha,17beta-diol (5betaA) by means of gas chromatography/combustion/isotopic ratio mass spectrometry (GC/C/IRMS). The within-assay and between-assay precision S.D.s of the investigated steroids were lower than 0.3 and 0.6parts per thousand, respectively. A comparative study on a population composed of 20 subjects has shown that the differences of the intra-individual delta(13)C-values for 16(5alpha)-androsten-3alpha-ol and 5beta-pregnane-3alpha,20alpha-diol are less than 0.9%. Thereafter, the method has been applied in the frame of an excretion study following oral ingestion of 50 mg DHEA initially and oral ingestion of 50 mg pregnenolone 48 h later. Our findings show that administration of DREA does not affect the isotopic ratio values of 16(5alpha)-androsten-3alpha-ol and 5beta-pregnane-3alpha,20alpha-diol, whereas the isotopic ratio values of 5beta-pregnane-3alpha,20alpha-diol vary by more 5parts per thousand upon ingestion of pregnenolone. We have observed delta(13)C-value changes lower than 1parts per thousand for 16(5alpha)-androsten-3alpha-ol, though pregnenolone is a precursor of the 16-ene steroids. In contrast to 5beta-pregnane-3alpha,20alpha-diol, the 16-ene steroid may be used as an endogenous reference compound when pregnenolone is administered. (C) 2004 Elsevier B.V. All rights reserved.