Inter‐individual variation of the urinary steroid profiles in Swedish and Norwegian athletes

The steroidal module of the Athlete Biological Passport (ABP) aims to detect doping with endogenous steroids, e.g. testosterone (T), by longitudinally monitoring several biomarkers. These biomarkers are ratios combined of urinary concentrations of testosterone and metabolically related steroids. However, it is evident after five years of monitoring steroid passports, that there are large variations in the steroid ratios complicating its interpretation. In this study, we used over 11 000 urinary steroid profiles from Swedish and Norwegian athletes to determine both the inter‐ and intra‐individual variations of all steroids and ratios in the steroidal passport. Furthermore, we investigated if the inter‐individual variations could be associated with factors such as gender, type of sport, age, time of day, time of year and if the urine was collected in or out of competition. We show that there are factors reported in today's doping tests that significantly affect the steroid profiles. The factors with the largest influence on the steroid profile was what type of sport classification the athlete belonged to as well as if the urine was collected in or out of competition. There were also significant differences based on what time of day and time of year the urine sample was collected. If these significant changes are relevant when longitudinally monitoring athletes in the steroidal module of the ABP, has to be further evaluated.