Atypical excretion profile and GC/C/IRMS findings may last for nine months after a single dose of nandrolone decanoate

• There were large inter-individual variation in the urinary excretion profile of nandrolone and its metabolites after the administration of nandrolone decanoate.
• Six and three of eleven individuals were identified as adverse analytical findings 120 and 270 days after the injection of only one single dose nandrolone decanoate.
• GC/C/IRMS confirmed the presence of exogenous 19-norandrosterone long time after the administration, even in a sample below the WADA decision limit.

The use of the anabolic androgenic steroid nandrolone and its prohormones is prohibited in sport. A common route of nandrolone administration is intramuscular injections of a nandrolone ester. Here we have investigated the detection time of nandrolone and 19-norandrosterone and 19-noretiocholanolone metabolites in eleven healthy men after the administration of a 150 mg dose of nandrolone decanoate. The urinary concentrations of nandrolone and the metabolites were monitored by GC–MS/MS for nine months and in some samples the presence of 19-norandrosterone was confirmed by GC/C/IRMS analysis. The participants were genotyped for polymorphisms in PDE7B1 and UGT2B15 genes previously shown to influence the activation and inactivation of nandrolone decanoate. There were large inter-individual variations in the excretion rate of nandrolone and the metabolites, although not related to genetic variations in the UGT2B15 (rs1902023) and PDE7B1 (rs7774640) genes. After the administration, 19-norandrosterone was found at 2-8-fold higher concentrations than 19-noretiocholanolone. We showed that nandrolone doping can be identified 4 and 9 months after the injection of only one single dose in six and three individuals, respectively. We also noted that GC/C/IRMS confirms the presence of exogenous 19-norandrosterone in the urine samples, showing δ13 values around −32 ‰. This was true even in a sample that was not identified as an atypical finding after the GC–MS/MS analysis further showing the power of using GC/C/IRMS in routine anti-doping settings.