Sensitive detection of testosterone and testosterone prohormone administrations based on urinary concentrations and carbon isotope ratios of androsterone and etiocholanolone.

The testing strategy for the detection of testosterone (T) or T-prohormones is based on the longitudinal evaluation of urinary steroid concentrations accompanied by subsequent isotope ratio mass spectrometry (IRMS)-based confirmation of samples showing atypical concentrations or concentration ratios. In recent years, the IRMS methodology focussed more and more on T itself and on the metabolites of T, 5α- and 5β-androstanediol. These target analytes showed the best sensitivity and retrospectivity, but their use has occasionally been challenging due to their comparably low urinary concentrations. Conversely, the carbon isotope ratios (CIR) of the main urinary metabolites of T, androsterone (A) and etiocholanolone (EITO), can readily be measured even from low urine volumes; those however, commonly offer a lower sensitivity and shorter retrospectivity in uncovering T misuse. Within this study, the CIRs of A and ETIO were combined with their urinary concentrations, resulting in a single parameter referred to as 'difference from weighted mean' (DWM). Both glucuronidated and sulfated steroids were investigated, encompassing a reference population (n = 110), longitudinal studies on three individuals, influence of ethanol in two individuals, and re-analysis of several administration studies including T, dihydrotestosterone, androstenedione, epiandrosterone, dehydroepiandrosterone, and T-gel. Especially DWM calculated for the sulfoconjugated steroids significantly prolonged the detection time of steroid hormone administrations when individual reference ranges were applied. Administration studies employing T encompassing CIR common for Europe (-23.8‰ and -24.4‰) were investigated and, even though for a significantly shorter time period and less pronounced, DWM could demonstrate the exogenous source of T metabolites.