Longitudinal evaluation of multiple biomarkers for the detection of testosterone gel administration in women with normal menstrual cycle

Effectiveness of blood steroidal passport markers for detecting testosterone abuse in Asians

The World Anti-Doping Agency (WADA) has introduced an Athlete Biological Passport (ABP) with a steroidal module, which is intended for the monitoring of longitudinal profiles of an athlete's steroid variables in urine to identify endogenous anabolic androgenic steroids that are administered exogenously. It has been in use since 2014. The prevalence of UGT2B17 gene deletion with relatively low levels of testosterone (T) glucuronide in urine is high in the Asian region. There are cases in which urinary T is below the detection limit in specific urine samples, for example, diluted urine, urine collected from females, or urine collected from UGT2B17 deletion individuals. Additional steroid markers T, 4-androstenedione (A4), and the T/A4 ratio in serum were newly added to the ABP steroidal module by WADA in 2023 to compensate for the urine steroid profile. In this study, populations of blood steroid markers in Asians (n = 510) were investigated and classified according to UGT2B17 polymorphism to confirm the effectiveness of blood steroid markers in monitoring Asian athletes. No significant difference in the T/A4 ratio was observed between the genotypes. Furthermore, an administration study of T enanthate in females (n = 10) who were classified according to UGT2B17 genotypes was performed. The concentration of T and the T/A4 ratio were found to be significantly increased in all post-administration samples until 15 days after administration (p < 0.01). The overall results supported the high effectiveness of subject-based monitoring for serum T and T/A4 ratio for recently identified shortcomings in the detection of T abuse in Asians.

Comparison of analytical approaches for the detection of oral testosterone undecanoate administration in men

For antidoping laboratories, the determination of an illicit testosterone (T) administration in urine samples remains a difficult process as it requires the determination of the exogenous origin by carbon isotope ratios (CIRs) of testosterone and its metabolites. As a complement to the urinary analysis, targeting testosterone esters (e.g. testosterone undecanoate [TU]) in serum samples by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) could represent a simpler approach compared with isotope ratio mass spectrometry (IRMS). These two approaches both lead to the direct detection of the administration of exogenous T but with a difference in effort and complexity of the analysis. To compare the detection window obtained with the two strategies, serum and the corresponding urine samples collected from an administration study with oral TU were analysed. Results showed that, at all timepoints where the intact TU was detected in serum, the CIRs of urinary steroids were also not in agreement with an endogenous origin. IRMS analysis required more effort but resulted in slightly longer detection windows than the ester analysis. Finally, this comparison study showed that, in the presence of a suspicious urinary steroid profile, the LC-MS/MS steroid esters analysis in the corresponding serum samples can be very helpful. If steroid esters are not detected, the IRMS analysis can then be conducted on the urine sample afterwards. Overall, the combination of matrices might facilitate the detection of prohibited T administration in sports, especially for athletes with naturally low T/E ratios.

Recent advances in mass spectrometry for the detection of doping

INTRODUCTION

The analysis of doping control samples is preferably performed by mass spectrometry, because obtained results meet the highest analytical standards and ensure an impressive degree of reliability. The advancement in mass spectrometry and all its associated technologies thus allow for continuous improvements in doping control analysis.

AREAS COVERED

Modern mass spectrometric systems have reached a status of increased sensitivity, robustness, and specificity within the last decade. The improved sensitivity in particular has, on the other hand, also led to the detection of drug residues that were attributable to scenarios where the prohibited substances were not administered consciously but rather by the unconscious ingestion of or exposure to contaminated products. These scenarios and their doubtless clarification represent a great challenge. Here, too, modern MS systems and their applications can provide good insights in the interpretation of dose-related metabolism of prohibited substances. In addition to the development of new instruments itself, software-assisted analysis of the sometimes highly complex data is playing an increasingly important role and facilitating the work of doping control laboratories.

EXPERT OPINION

The sensitive analysis and evaluation of a higher number of samples in a shorter time is made possible by the ongoing developments in mass spectrometry.

Influence of ethanol consumption and food intake on serum concentrations of endogenous steroids

Steroid biosynthesis and biotransformation are based on a cascade of enzymatic processes being highly sensitive to various external influences. Amongst those, ethanol was shown to affect testosterone metabolism. For doping analyses, athlete steroid profiles comprise seven urinary steroid metabolites, of which relevant ratios are significantly increased following ethanol consumption. This effect is presumably based on the lack of hepatic NAD+-coenzyme as a consequence of ethanol oxidation. Only recently, testosterone (T) and androstenedione (A4) blood profiles have been introduced as additional approach for doping control. However, a potential influence of ethanol intake on testosterone biosynthesis and thus on blood steroid profiles has not been investigated so far. Therefore, steroid concentrations from 10 males and 10 females receiving an ethanol infusion up to a breath alcohol concentration of 0.5 mg/L which was hold as a plateau for two hours were conducted. Blood samples were drawn every 15 min for steroid quantification. An ethanol-dependent T/A4 increase up to 385% resulting from A4 suppression was observed in 14 volunteers. In addition, we observed sporadic A4 increases coinciding with cortisol and ACTH pulses pointing to a meal-induced adrenal stimulation. While testosterone levels in males showed diurnal variation solely, testosterone levels in some females were found to be susceptible to ethanol- and ACTH-dependent perturbations, which is thought to be due to its predominant adrenal synthesis in females. In conclusion, the results of the present study emphasize the importance of blood sampling at a sufficient time interval from food and ethanol intake. This is of interest if T and A4 are used for diagnostics in doping control.

Contemporary blood doping-Performance, mechanism, and detection

Blood doping is prohibited for athletes but has been a well-described practice within endurance sports throughout the years. With improved direct and indirect detection methods, the practice has allegedly moved towards micro-dosing, that is, reducing the blood doping regime amplitude. This narrative review evaluates whether blood doping, specifically recombinant human erythropoietin (rhEpo) treatment and blood transfusions are performance-enhancing, the responsible mechanism as well as detection possibilities with a special emphasis on micro-dosing. In general, studies evaluating micro-doses of blood doping are limited. However, in randomized, double-blinded, placebo-controlled trials, three studies find that infusing as little as 130 ml red blood cells or injecting 9 IU × kg bw-1 rhEpo three times per week for 4 weeks improve endurance performance ~4%-6%. The responsible mechanism for a performance-enhancing effect following rhEpo or blood transfusions appear to be increased O2 -carrying capacity, which is accompanied by an increased muscular O2 extraction and likely increased blood flow to the working muscles, enabling the ability to sustain a higher exercise intensity for a given period. Blood doping in micro-doses challenges indirect detection by the Athlete Biological Passport, albeit it can identify ~20%-60% of the individuals depending on the sample timing. However, novel biomarkers are emerging, and some may provide additive value for detection of micro blood doping such as the immature reticulocytes or the iron regulatory hormones hepcidin and erythroferrone. Future studies should attempt to validate these biomarkers for implementation in real-world anti-doping efforts and continue the biomarker discovery.

Evaluation of sulfate metabolites as markers of topical testosterone administration in Caucasian and Asian populations

Sulfate metabolites of endogenous anabolic androgenic steroids (EAAS) have been shown to prolong the detection times compared with the conventional urinary markers of the steroid profile for oral and intramuscular administrations of testosterone (T). In this work, the sensitivity of sulfate EAAS markers for the detection of T gel administration has been evaluated in six Caucasian and six Asian male volunteers. Fourteen sulfate metabolites were measured in basal and post-administration samples after multiple doses of T gel (100 mg/day, three consecutive days), and the detection times based on individual thresholds for each volunteer were evaluated. Sulfate concentrations did not show adequate sensitivity, but the results of sulfate ratios were much more promising. Androsterone sulfate/testosterone sulfate (A-S/T-S), epiandrosterone sulfate/epitestosterone sulfate (epiA-S/E-S), epiA-S/T-S, and etiocholanolone sulfate/epitestosterone sulfate (Etio-S/E-S) provided the most consistent detectability for all volunteers and populations, with detection times ranging from 60 to 96 h since the first dose. Additional ratios improved detectability to up to 7 days, but only in particular volunteers. In general, sensitivity was similar to or better than the conventional testosterone/epitestosterone ratio (T/E) of the steroid profile, which further reinforces the conclusion that sulfate EAAS metabolites can be a good complement for the current steroid profile.

A new multimodal paradigm for biomarkers longitudinal monitoring: a clinical application to women steroid profiles in urine and blood

BACKGROUND

Most current state-of-the-art strategies to generate individual adaptive reference ranges are designed to monitor one clinical parameter at a time. An innovative methodology is proposed for the simultaneous longitudinal monitoring of multiple biomarkers. The estimation of individual thresholds is performed by applying a Bayesian modeling strategy to a multivariate score integrating several biomarkers (compound concentration and/or ratio). This multimodal monitoring was applied to data from a clinical study involving 14 female volunteers with normal menstrual cycles receiving testosterone via transdermal route, as to test its ability to detect testosterone administration. The study samples consisted of urine and blood collected during 4 weeks of a control phase and 4 weeks with a daily testosterone gel application.

RESULTS

Integrating multiple biomarkers improved the detection of testosterone gel administration with substantially higher sensitivity compared with the distinct follow-up of each biomarker, when applied to selected urine and serum steroid biomarkers, as well as the combination of both. Among the 175 known positive samples, 38% were identified by the multimodal approach using urine biomarkers, 79% using serum biomarkers and 83% by combining biomarkers from both biological matrices, whereas 10%, 67% and 64% were respectively detected using standard unimodal monitoring.

SIGNIFICANCE AND NOVELTY

The detection of abnormal patterns can be improved using multimodal approaches. The combination of urine and serum biomarkers reduced the overall number of false-negatives, thus evidencing promising complementarity between urine and blood sampling for doping control, as highlighted in the case of the use of transdermal testosterone preparations. The generation in a multimodal setting of adaptive and personalized reference ranges opens up new opportunities in clinical and anti-doping profiling. The integration of multiple parameters in a longitudinal monitoring is expected to provide a more complete evaluation of individual profiles generating actionable intelligence to further guide sample collection, analysis protocols and decision-making in clinics and anti-doping.

Longitudinal Profiling of Endogenous Steroids in Blood Using the Athlete Biological Passport Approach

CONTEXT

Detection of endogenous anabolic androgenic steroids (EAAS), like testosterone (T), as doping agents has been improved with the launch of the Steroidal Module of the Athlete Biological Passport (ABP) in urine samples.

OBJECTIVE

To target doping practices with EAAS, particularly in individuals with low level of biomarkers excreted in urine, by including new target compounds measured in blood.

DESIGN

T and T/androstenedione (T/A4) distributions were obtained from 4 years of anti-doping data and applied as priors to analyze individual profiles from 2 T administration studies in female and male subjects.

SETTING

Anti-doping laboratory. Elite athletes (n = 823) and male and female clinical trials subjects (n = 19 and 14, respectively).

INTERVENTION(S)

Two open-label administration studies were carried out. One involved a control phase period followed by patch and then oral T administration in male volunteers and the other followed female volunteers during 3 menstrual cycles with 28 days of daily transdermal T application during the second month.

MAIN OUTCOME MEASURE(S)

Serum samples were analyzed for T and A4 and the performance of a longitudinal ABP-based approach was evaluated for T and T/A4.

RESULTS

An ABP-based approach set at a 99% specificity flagged all female subjects during the transdermal T application period and 44% of subjects 3 days after the treatment. T showed the best sensitivity (74%) in response to transdermal T application in males.

CONCLUSIONS

Inclusion of T and T/A4 as markers in the Steroidal Module can improve the performance of the ABP to identify T transdermal application, particularly in females.

Variability of the urinary and blood steroid profiles in healthy and physically active women with and without oral contraception

The steroidal module of the athlete biological passport (ABP) targets the use of pseudo-endogenous androgenous anabolic steroids in elite sport by monitoring urinary steroid profiles. Urine and blood samples were collected weekly during two consecutive oral contraceptive pill (OCP) cycles in 15 physically active women to investigate the low urinary steroid concentrations and putative confounding effect of OCP. In urine, testosterone (T) and epitestosterone (E) were below the limit of quantification of 1 ng/ml in 62% of the samples. Biomarkers' variability ranged between 31% and 41%, with a significantly lesser variability for ratios (except for T/E [41%]): 20% for androsterone/etiocholanolone (p < 0.001) and 25% for 5α-androstane-3α,17β-diol/5ß-androstane-3α,17β-diol (p < 0.001). In serum, markers' variability (testosterone: 24%, androstenedione: 23%, dihydrotestosterone: 19%, and T/A4: 16%) was significantly lower than in urine (p < 0.001). Urinary A/Etio increased by >18% after the first 2 weeks (p < 0.05) following withdrawal blood loss. In contrast, serum T (0.98 nmol/l during the first week) and T/A4 (0.34 the first week) decreased significantly by more than 25% and 17% (p < 0.05), respectively, in the following weeks. Our results outline steroidal variations during the OCP cycle, highlighting exogenous hormonal preparations as confounder for steroid concentrations in blood. Low steroid levels in urine samples have a clear negative impact on the subsequent interpretation of steroid profile of the ABP. With a greater analytical sensitivity and lesser variability for steroids in healthy active women, serum represents a complementary matrix to urine in the ABP steroidal module.

Disposition of serum steroids in response to combined oral contraceptives and menstrual cycle phases: A double-blind, randomized, placebo-controlled study

To analyze doping control samples from female athletes demands understanding of non-doping factors that affect the steroid profile. These could be physiological factors such as exercise, alcohol consumption, hormonal changes during the menstrual cycle, or the effect of commonly used approved drugs like combined oral contraceptives. Urine samples have been the main way of doping testing, but serum samples are proposed as a complement. Testosterone, dihydrotestosterone, or the ratio of testosterone and androstenedione has been proposed as a biomarker for testosterone doping because it increases after transdermal testosterone administration. In this double-blind, randomized, placebo-controlled study of 340 healthy females, we analyzed the serum steroid levels, including glucuronide metabolites, before and after 3 months of combined oral contraceptives or placebo. At follow up, sample collection in the placebo group was randomly distributed between different menstrual cycle phases. This enabled to analyze changes in concentrations between the follicular, ovulation, and luteal phases. Combined oral contraceptives decreased all serum steroids including the glucuronide metabolites. As expected, serum testosterone levels increased during the ovulation phase, and also androstenedione and androstenediol, whereas the glucuronide metabolites remained unaffected. Neither combined oral contraceptives nor menstrual cycle phases did affect the ratio of testosterone and androstenedione in serum, and consequently this ratio seems promising as a marker of doping with endogenous anabolic androgenic steroids in women.

Trans Dermal Testosterone Compared to Intramuscular Testosterone for Young Males with Delayed Puberty: A PRISMA Guided Systematic Review

Background

Challenges in selecting the right formulation of testosterone (TE) for young males with delayed puberty (DP) arise from the fact that there is limited evidence based guidelines in recommending the most efficient and safe formulation of TE.

Objective

To evaluate the existing evidence and systematically review the interventional effects of transdermal TE to other modes of TE administration for the treatment of DP among young and adolescent males.

Methods

All types of methodologies published in English were searched from the data sources including MEDLINE, Embase, Cochrane Reviews, Web of Science, AMED and Scopus from 2015 till 2022. Boolean operators with keywords "types of TE", "modes of TE administration", "DP", "transdermal TE", "constitutional delay of growth and puberty, (CDGP)" "adolescent boys" and "hypogonadism" to optimize the search results. The main outcomes of concern were optimal serum TE level, body mass index, height velocity, testicular volume, pubertal stage (Tanner), The secondary outcomes included in this study were adverse events and patient satisfaction.

Results

After screening 126 articles, 39 full texts were reviewed. Only five studies could be included after careful screening and rigid quality assessments. Most studies were at high or unclear risk of bias with short duration and follow up periods. Only one study was a clinical trial covering all the outcomes of interests.

Conclusion

This study points out the favorable effects of transdermal TE treatment for DP in boys, while the existence of the vast gap in research needs to be acknowledged. Despite the utmost demand in an appropriate TE treatment for young males with DP, scarce efforts and trials are being undertaken to provide clear clinical guidance of treatment. Quality of life, cardiac events, metabolic parameters, coagulation profiles are important aspects of the treatment are overlooked and under evaluated in most studies.

Systematic Review Registration

PROSPERO CRD 42022369699.

Usefulness of serum androgen isotope ratio mass spectrometry (IRMS) to detect testosterone supplementation in women

The detection of testosterone intake is facilitated by monitoring the urinary steroid profile in the athlete biological passport. This technique can be used with confidence to identify target samples for isotope ratio mass spectrometry. Regrettably, most research has been performed on male subjects resulting in a method that does not account for females' steroid concentration and/or variation. This study evaluates the usefulness of the carbon isotope ratio (CIR) in serum of female subjects. Two steroid sulphates are targeted in serum, androsterone and epiandrosterone. Both exhibit statistically significant depletion of their CIR after 10 weeks of daily (10 mg) transdermal testosterone administration. Of the 21 female subjects, samples from six individuals were identified as adverse analytical findings; additionally, four were found atypical considering the serum CIR. The urinary athlete biological passport was not sufficiently sensitive to identify target serum samples for isotope ratio mass spectroscopy. Of the six with a suspicious passport, only two could be confirmed using the serum CIR of androsterone and epiandrosterone. This study shows that CIR analysis in serum cannot be considered the sole confirmatory solution to detect testosterone doping in women due to low sensitivity. However, this analysis has the potential to be used as a complementary method in certain situations to confirm exogenous testosterone in women.

Future opportunities for the Athlete Biological Passport

The Athlete Biological Passport (ABP) was introduced to complement the direct anti-doping approach by indirectly outlining the possible use of prohibited substances or methods in sports. The ABP proved its effectiveness, at least through a deterrent effect, even though the matrices used for longitudinal monitoring (urine and blood) are subject to many intrinsic (e.g., genetic) and extrinsic (e.g., environmental conditions) confounding factors. In that context, new and more specific biomarkers are currently under development to enhance both the sensitivity and the specificity of the ABP. Multiple strategies are presently being explored to improve this longitudinal monitoring, with the development of the current modules, the investigation of new strategies, or the screening of new types of doping. Nevertheless, due to the variability induced by indirect biomarkers, the consideration of confounding factors should continuously support this research. Beyond tremendous advances in analytical sensitivity, machine learning-based approaches seem inevitable to facilitate an expert interpretation of numerous biological profiles and promote anti-doping efforts. This perspective article highlights the current innovations of the Athlete Biological Passport that seem the most promising. Through different research axes, this short manuscript provides an opportunity to bring together approaches that are more widely exploited (e.g., omics strategies) and others in the early stages of investigation (e.g., artificial intelligence) seeking to develop the ABP.

Agreement of steroid profiles in Athlete Biological Passport residues and corresponding serum samples

The steroid module of the Athlete Biological Passport (ABP) is based on the analysis of six endogenous steroids in urine samples and a Bayesian statistical approach. However, the urinary steroid concentrations may be affected by confounders like microbial degradation, possible co-administration of diuretics as masking agents, insufficient conjugate hydrolysis or UGT2B17 gene polymorphisms affecting glucuronidation. Therefore, it can be helpful to use other matrices (ABP blood and serum samples) to quantify steroids and thereby support noticeable deviations in the Athlete Biological Passport, for example, abnormally increased urinary testosterone/epitestosterone (T/E) ratios. Aim of the study was to investigate the feasibility to re-use plasma obtained from athlete ABP blood samples for measuring a steroid profile. Therefore, testosterone, androstenedione, cortisol and cortisone were quantified in 36 intra-individual matching ABP blood and serum samples. The steroid levels measured in both matrices showed a high agreement indicating a good stability uninfluenced by storage temperature and duration. Our results pointed out the possibility to expand the athlete ABP blood analysis for steroid profiling.

Klotho Polymorphism in Association With Serum Testosterone and Knee Strength in Women After Testosterone Administration

Administration of testosterone (T) is associated with increased serum T concentrations and improved physical performance in women. However, the inter-individual variation in T concentrations after T treatment is large and may in part be due to genetic variations. Serum T, as well as dihydrotestosterone (DHT), androstenedione (A) and the T/A ratio have been suggested as promising doping biomarkers for testosterone intake. Here, polymorphisms in androgen metabolic enzyme genes have been investigated in healthy women prior to and after 10 weeks administration of testosterone cream. Klotho is a protein that has been associated with anaerobic strength and here a genetic variation in klotho gene was studied in relation to performance as measured by isokinetic knee strength, as well as to serum androgen disposition. The AKR1C3 genotype (rs12529) was associated with serum T levels at baseline, whereas serum concentrations post T treatment did not differ between genotypes. The SLCO2B1 (rs12422149) and UGT2B17 deletion polymorphisms were not associated with serum concentration of either T, DHT or A. The klotho polymorphism (rs9536314) was associated with serum concentrations of both total T and T/A ratio after T administration. Individuals with the GT genotype increased T concentrations and T/A ratio more than women homozygous for the T allele. No significant difference in the association of klotho genotype with knee muscle strength was observed between placebo and T treatment. However, individuals homozygous for the T allele showed higher isometric mean torque scores at exit than GT subjects after T administration. This is the first time a genotype has been associated with androgen concentrations after T administration and muscle strength in women. Our results imply that subjects with a polymorphism in klotho may be more prone to detection using serum T and A as biomarkers.

Detection of testosterone microdosing in healthy females

The ready detectability of synthetic androgens by mass spectrometry (MS)-based antidoping tests has reoriented androgen doping to using testosterone (T), which must be distinguished from its endogenous counterpart making detection of exogenous T harder. We investigated urine and serum steroid and hematological profiling individually and combined to determine the optimal detection model for T administration in women. Twelve healthy females provided six paired blood and urine samples over 2 weeks prior to treatment consisting of 12.5-mg T in a topical transdermal gel applied daily for 7 days. Paired blood and urine samples were then obtained at the end of treatment and Days 1, 2, 4, 7, and 14 days later. Compliance with treatment and sampling was high, and no adverse effects were reported. T treatment significantly increased serum and urine T, serum dihydrotestosterone (DHT), urine 5α-androstane-3α,17β-diol (5α-diol) epitestosterone (E), and urine T/E ratio with a brief window of detection (2-4 days) as well as total and immature (medium and high fluorescence) reticulocytes that remained elevated over the full 14 posttreatment days. Carbon isotope ratio MS and the OFF score and Abnormal Blood Profile score (ABPS) were not discriminatory. The optimal multivariate model to identify T exposure combined serum T, urine T/E ratio with three hematological variables (% high fluorescence reticulocytes, mean corpuscular hemoglobin, and volume) with the five variables providing 93% correct classification (4% false positive, 10% false negatives). Hence, combining select serum and urine steroid MS variables with reticulocyte measures can achieve a high but imperfect detection of T administration to healthy females.

Annual banned-substance review: Analytical approaches in human sports drug testing 2020/2021

Most core areas of anti-doping research exploit and rely on analytical chemistry, applied to studies aiming at further improving the test methods' analytical sensitivity, the assays' comprehensiveness, the interpretation of metabolic profiles and patterns, but also at facilitating the differentiation of natural/endogenous substances from structurally identical but synthetically derived compounds and comprehending the athlete's exposome. Further, a continuously growing number of advantages of complementary matrices such as dried blood spots have been identified and transferred from research to sports drug testing routine applications, with an overall gain of valuable additions to the anti-doping field. In this edition of the annual banned-substance review, literature on recent developments in anti-doping published between October 2020 and September 2021 is summarized and discussed, particularly focusing on human doping controls and potential applications of new testing strategies to substances and methods of doping specified in the World Anti-Doping Agency's 2021 Prohibited List.

Steroid profiling by UHPLC-MS/MS in dried blood spots collected from healthy women with and without testosterone gel administration

The quantification of a large panel of endogenous steroids in serum by LC-MS/MS represents a powerful clinical tool for the screening or diagnosis of diverse endocrine disorders. This approach has also demonstrated excellent sensitivity for the detection of testosterone misuse in the anti-doping field, especially in female athlete population. In both situations, the use of dried blood spots (DBS) could provide a viable alternative to invasive venous blood collection. Here, the evaluation of DBS sampling for the quantification of a panel of endogenous steroids using UHPLC-MS/MS is described. The UHPLC-MS/MS method was validated for quantitative analysis of eleven free and eight conjugated steroids and was then used for the analysis of DBS samples collected in 14 healthy women during a normal menstrual cycle (control phase) followed by a 28-days testosterone gel treatment (treatment phase). Results were compared with those obtained from serum matrix. Satisfactory performance was obtained for all compounds in terms of selectivity, linearity, accuracy, precision, combined uncertainty, stability as well as extraction recovery and matrix effects. In control phase, high correlation was observed between DBS and serum concentrations for most compounds. In treatment phase, higher testosterone concentrations were observed in capillary than in venous DBS, suggesting a possible interference resulting from testosterone contamination on finger(s) used for gel application. Steroid profiling in capillary DBS represents a simple and efficient strategy for monitoring endogenous steroid concentrations and their fluctuation in clinical context of steroid-related disorders, or for the detection of testosterone abuse in anti-doping.

Carbon isotope ratios of endogenous steroids found in human serum-method development, validation, and reference population-derived thresholds

In order to detect the misuse of testosterone (T), urinary steroid concentrations and concentration ratios are quantified and monitored in a longitudinal manner to enable the identification of samples exhibiting atypical test results. These suspicious samples are then forwarded to isotope ratio mass spectrometry (IRMS)–based methods for confirmation. Especially concentration ratios like T over epitestosterone (E) or 5α-androstanediol over E proved to be valuable markers. Unfortunately, depending on the UGT2B17 genotype and/or the gender of the athlete, these markers may fail to provide evidence for T administrations when focusing exclusively on urine samples. In recent years, the potential of plasma steroids has been investigated and were found to be suitable to detect T administrations especially in female volunteers. A current drawback of this approach is the missing possibility to confirm that elevated steroid concentrations are solely derived from an administration of T and cannot be attributed to confounding factors. Therefore, an IRMS method for plasma steroids was developed and validated taking into account the comparably limited sample volume. As endogenous reference compounds, unconjugated cholesterol and dehydroepiandrosterone sulfate were found suitable, while androsterone and epiandrosterone (both sulfo-conjugated) were chosen as target analytes. The developed method is based on multi-dimensional gas chromatography coupled to IRMS in order to optimize the overall assay sensitivity. The approach was validated, and a reference population encompassing n = 65 males and females was investigated to calculate population-based thresholds. As proof-of-concept, samples from volunteers receiving T replacement therapies and excretion study samples were investigated.