Intra‐Individual Variability of Blood and Urinary Steroid Markers and the Response to Codeine Intake in Healthy Men and Women

In this study, intra-individual variation of serum and urinary Athlete Biological Passport (ABP) steroids was investigated in relation to 3 days of codeine intake in healthy men and women. Two study populations were included: (a) 14 participants evaluated for longitudinal variation over 6 weeks, and (b) 11 participants evaluated for variation within 1 week and following 24 and 72 h of daily codeine intake. Urinary and serum steroid concentrations were analyzed using WADA-accredited GC-MS/MS and LC-MS/MS methods, respectively. To study the longitudinal changes of the ABP hormones after codeine intake, individual thresholds were calculated as the mean ± 3 SD of three baseline values. During the 6-week observation period, the variability of serum markers ranged from 3% to 34%. Comparable variability was observed when serum markers were measured on three occasions within 1 week prior to codeine administration. Codeine intake did not significantly affect the median urinary and serum steroid concentrations. Urinary T/E was elevated in five subjects, whereas for two participants, the serum T decreased below the individual calculated thresholds. The changes were observed in both male and female participants. The atypical serum T profiles were accompanied by stable T/A4. Marked inter-individual variability was observed in urinary concentrations of codeine and its active metabolite morphine; nevertheless, all participants would have tested negative for morphine in an in-competition setting. These results show that both the urinary and serum steroid profiles may be perturbed already after 1-3 days of codeine use.