Anabolic steroids in livestock production: Background and implications for chemical food safety.

The use of steroids in livestock animals is a source of concern for consumers because of the risks associated with the presence of their residues in foodstuffs of animal origin. Technological advances such as mass spectrometry have made it possible to play a fundamental role in controlling such practices, firstly for the discovery of marker metabolites but also for the monitoring of these compounds under the regulatory framework. Current control strategies rely on the monitoring of either the parent drug or its metabolites in various matrices of interest. As some of these steroids also have an endogenous status specific strategies have to be applied for control purposes. This review aims to provide a comprehensive and up-to-date knowledge of analytical strategies, whether targeted or non-targeted, and whether they focus on markers of exposure or effect in the specific context of chemical food safety regarding the use of anabolic steroids in livestock. The role of new approaches in data acquisition (e.g. ion mobility), processing and analysis, (e.g. molecular networking), is also discussed.

On-site monitoring of nandrolone in cattle farming samples by portable atmospheric pressure chemical ionization mass spectrometry with ambient sampling.

Nandrolone (NT) is a type of androgen anabolic steroid that is often illegally used in cattle farming, leading to unpredictable harm to human health via the food chain. In this study, a rapid detection method for NT in the samples of cattle farming was established using a portable mass spectrometer. The instrument parameters were optimized, including a thermal desorption temperature of 220 °C, a pump speed of 30 %, an APCI ionization voltage of 3900 v, and an injection volume of 6 µL. The samples of bovine urine, feed, sewage, and tissue were selected, and extracted using a solution of methanol:acetonitrile (1:1, v/v), followed by spiking a NT standard solution (1000 ng·mL-1) and ionization through the APCI ion source for detection. The results showed that NT could not be detected in beef and feed due to the complexity of the matrix, while clear signals of NT ions were observed in bovine urine and sewage samples, with LODs of 1000 and 100 ng·mL-1, respectively. Furthermore, quantitative analysis was attempted, and a good linear relationship (R2 = 0.9952) was observed for NT in sewage within the range of 100 to 1000 ng·mL-1. At spiked levels of 100, 500, 1000 and 2000 ng mL-1, the recovery rates ranged from 74.3 % to 92.8 %, with a relative standard deviation (n = 6) of less than 15 %. In conclusion, this detection method offers the advantages of simplicity, rapidity, strong timeliness, and specificity, making it suitable for on-site detection. It can be used for qualitative screening of nandrolone in bovine urine and quantitative analysis of nandrolone in sewage.

Investigation of in vitro generated metabolites of LGD-4033, a selective androgen receptor modulator, in homogenized camel liver for anti-doping applications.

RATIONALE: The use of selective androgen receptor modulators (SARM) in sports is prohibited by the World Anti-Doping Agency (WADA) due to their potential as performance-enhancing drugs, offering an unfair advantage. LGD-4033 is a SARM known for its similarities to anabolic steroids and can be easily purchased online, leading to increased availability and misuse. Adverse analytical findings have revealed the presence of SARMs in dietary supplements. Although LGD-4033 misuse has been reported in human sports over the years, concerns also arise regarding its illicit use in animal sports, including camel racing. Although various studies have investigated the metabolism of LGD-4033 in humans, horse, and other species, there is limited research specifically dedicated to racing camels. METHODS: This study focuses on the in vitro metabolism of LGD-4033 in homogenized camel liver using liquid chromatography-high-resolution mass spectrometry (LC-HRMS) to identify and characterize the metabolites. RESULTS: The findings indicated the presence of 12 phase I metabolites and 1 phase II metabolite. Hydroxylation was responsible for the formation of the main phase I metabolites that were identified. A glucuronic acid conjugate of the parent drug was observed in this study, but no sulfonic acid conjugate was found. The possible chemical structures of these metabolites, along with their fragmentation patterns, were identified using MS. CONCLUSIONS: These findings provide valuable insights into the metabolism of LGD-4033 in camels and aid in the development of effective doping control methods for the detection of SARMs in camel racing.

Using Proteins As Markers for Anabolic Steroid Abuse: A New Perspective in Doping Control?

Drug toxicity is a major concern and has motivated numerous studies to elucidate specific adverse mechanisms, with acetaminophen being the favorite candidate in toxicology studies. Conversely, androgenic anabolic steroids (AASs) also represent a severe public health issue in sports for elite and non-elite athletes. Supraphysiological dosages of AASs are associated with various adverse effects, from cardiovascular to neurological repercussions including liver dysfunction. Yet, few studies have addressed the toxicity of anabolic steroids, and a significant amount of work will be needed to elucidate and understand steroid toxicity properly. This Perspective suggests ideas on how proteomics and liquid chromatography coupled with high-resolution tandem mass spectrometry (LC-HRMS/MS) can contribute to (1) pinpoint serum proteins affected by substantial doses of anabolic steroids that would represent interesting novel candidates for routine testing and (2) provide additional knowledge on androgenic anabolic steroid toxicity to help raise awareness on the harmful effects.

Identification and Synthesis of Selected In Vitro Generated Metabolites of the Novel Selective Androgen Receptor Modulator (SARM) 2f.

Among anabolic agents, selective androgen receptor modulators (SARMs) represent a new class of potential drugs that can exhibit anabolic effects on muscle and bone with reduced side effects due to a tissue-selective mode of action. Besides possible medical applications, SARMs are used as performance-enhancing agents in sports. Therefore, they are prohibited by the World Anti-Doping Agency (WADA) in and out of competition. Since their inclusion into the WADA Prohibited List in 2008, there has been an increase in not only the number of adverse analytical findings, but also the total number of SARMs, making continuous research into SARMs an ongoing topic in the field of doping controls. 4-((2R,3R)-2-Ethyl-3-hydroxy-5-oxopyrrolidin-1-yl)-2-(trifluoromethyl)benzonitrile (SARM 2f) is a novel SARM candidate and is therefore of particular interest for sports drug testing. This study describes the synthesis of SARM 2f using a multi-step approach, followed by full characterization using liquid chromatography-high-resolution mass spectrometry (LC-HRMS) and nuclear magnetic resonance spectroscopy (NMR). To provide the first insights into its biotransformation in humans, SARM 2f was metabolized using human liver microsomes and the microsomal S9 fraction. A total of seven metabolites, including phase I and phase II metabolites, were found, of which three metabolites were chemically synthesized in order to confirm their structure. Those can be employed in testing procedures for routine doping controls, further improving anti-doping efforts.

Gas chromatography properties and mass spectrometry fragmentation of anabolic androgenic steroids in doping control.

Aim: This study aimed to investigate the gas chromatographic properties and mass spectrometric fragmentations of anabolic androgenic steroids (AASs) after trimethylsilylated derivatization. Materials & methods: A total of 113 AASs were analyzed through gas chromatography-mass spectrometry in the full-scan mode. Results: New fragmentation pathways yielding m/z 129, 143 and 169 ions were analyzed. Based on the characteristics of the A-ring, seven classes of drugs were identified and analyzed. Conclusion: The fragmentation pathway of a new classification of 4-en-3-hydroxyl was reported for the first time. The relationship between the chemical structures of AASs and their retention time, along with their molecular ion peak abundance, was also reported herein for the first time.

Do you get what you see? The illicit doping market in Denmark-An analysis of performance and image enhancing drugs seized by the police over a 1-year period.

This study examines doping products seized by the police in three regional police districts in Denmark from December 2019 to December 2020. The products, often referred to as performance and image-enhancing drugs (PIEDs), are described in relation to the country of origin, manufacturing company, and the active pharmaceutical ingredient (API) stated on the packaging versus the one identified by subsequent chemical analysis. The study also includes a description of the degree of professionalism by which the products appear according to EU requirements. A total of 764 products were seized during the study period. The products originate from 37 countries, mainly located in Asia (37%), Europe (23%), and North America (13%). One hundred ninety-three different manufacturing companies could be identified from the product packaging. The most frequent compound class was the androgenic anabolic steroids, found in 60% of the products. In 25%-34% of the products, either no or an incorrect API relative to the one stated on the product was found. However, only 7%-10% contain either no API or a compound from a different compound class than the one stated. Most products had a professional appearance fulfilling most EU requirements for packaging information. The study shows that many different companies supply PIEDs to the Danish market and that counterfeit and substandard products are widespread. Many products do, however, appear professional to the user giving an impression of a high-quality product. Although many products are substandard, they most often contain an API from the same compound class as the one labeled.

Doping with testosterone and androgenic/anabolic steroids: Impact on health, screening tools and medical care.

Doping in elite or amateur athletes with testosterone, androgens and anabolic steroids (A/AS) has as a main objective to develop muscle strength and mass to improve sports performance. Massive doping is a worldwide public health issue insufficiently known by physicians in general and by endocrinologists in particular. Yet, its prevalence, probably underestimated, would be between 1 and 5% at the international level. Numerous deleterious effects associated with A/AS abuse have been identified: inhibition of the gonadotropic axis responsible for hypogonadotropic hypogonadism and infertility in men, and masculinization (defeminization), hirsutism and anovulation in women. Metabolic (very low HDL cholesterol), hematological (polycythemia), psychiatric, cardiovascular and hepatic complications have also been documented. As a result, anti-doping agencies have developed increasingly effective techniques for detecting A/AS, both to identify and punish cheating athletes and to protect the health of the greatest number of them. These techniques use a combination of liquid and gas chromatographic methods coupled with mass spectrometry, known respectively by the acronyms LC-MS and GC-MS. These detection tools have a remarkable sensitivity and specificity to detect natural steroids and synthetic A/AS of known structure. Furthermore, by distinguishing isotopes, it is also possible to distinguish natural endogenous hormones, testosterone and androgenic precursors from those administered for doping purposes. For elite athletes, a "biological passport" has also been introduced. It consists of monitoring the evolution of steroids and their metabolites, as well as other biological parameters in the blood and urine over time after having established a basal state athlete signature, established, a priori, without doping. Better training of health professionals, general practitioners and specialists should be a priority for academic institutions and medical societies. It would provide them with better knowledge of the populations at risk and the clinical and biological semiology of male and female doping, including withdrawal syndrome associated with anxiety and depression following cessation of chronic A/AS use. The ultimate goal is to provide these physicians with the keys to treating these patients while combining medical rigor and empathy. These points will be addressed in this short manuscript.

Evaluation of alternative gas chromatographic and mass spectrometric behaviour of trimethylsilyl-derivatives of non-hydrolysed sulfated anabolic steroids.

Sulfated metabolites have shown to have potential as long-term markers (LTMs) of anabolic-androgenic steroid (AAS) abuse. The compatibility of gas chromatography-mass spectrometry (GC-MS) with trimethylsilyl (TMS)-derivatives of non-hydrolysed sulfated steroids has been demonstrated, where, after derivatisation, generally, two closely eluting isomers are formed that both have the same molecular ion [M-H2 SO4 ]•+ . Sulfated reference standards are in limited commercial availability, and therefore, the current knowledge of the GC-MS behaviour of these compounds is mainly based on sulfating and analysing the available standard reference material. This procedure can unfortunately not cover all of the current known LTMs as these are often not available as pure substance. Therefore, in theory, some metabolites could be missed as they exhibit alternative behaviour. To investigate the matter, in-house sulfated reference materials that bear resemblance to known sulfated LTMs were analysed on GC-MS in their TMS-derivatised non-hydrolysed state. The (alternative) gas chromatographic and mass spectrometric behaviour was mapped, evaluated and linked to the corresponding steroid structures. Afterwards, using fraction collection, known sulfated LTMs were isolated from excretion urine to confirm the observed findings. The categories that were selected were mono-hydroxy-diones, 17-methyl-3,17-diols and 17-keto-3,16-diols as these are commonly encountered AAS conformations. The ability to predict the GC-MS behaviour of non-hydrolysed sulfated AAS metabolites is the corner stone of finding new metabolites. This knowledge is also essential, for example, for understanding AAS detection analyses, for the mass spectrometric characterization of metabolites of new designer steroids or when one needs to characterize an unknown steroid structure.

Metabolites identification of anabolic steroid bolasterone in vitro and in rats by high resolution liquid chromatography mass spectrometry.

Bolasterone (7α,17α-dimethyltestosterone) and anabolic androgenic steroids are included in the World Anti-Doping Agency's Prohibited list of substances. This study aimed to evaluate the metabolism of bolasterone through in vitro experiments using rat liver microsomes and in vivo experiments using rat urine after oral administration. Urine samples were collected over a 168-h period. Bolasterone and its metabolites were detected by liquid chromatography coupled with a Q-Exactive Obitrap mass spectrometry (LC-HRMS). Ultimately 16 hydroxylated metabolites (M1-M16), one metabolite from the reduction of the 3-keto function and 4-ene (M17), and one glucuronic acid conjugated metabolite (M18) were detected. Metabolites M17 and M18 were confirmed by comparison with available reference or authentic standards. Metabolic modifications in the structure of the parent bolasterone result in different fragmentation patterns. Based on the sensitivity of the HRMS data, characteristic ions such as m/z 121.064 (C8 H9 O) generated from ring A of the mono-hydroxylated metabolites and 121.101 (C9 H13 ) generated from ring D of the di-hydroxylated metabolites were observed that helped differentiate between the obtained metabolites. The structures of fragment ions were tentatively proposed based on their fragmentation pathways, where the significant ions were correlated to the possible structural fragments. In conclusion, new metabolites of bolasterone were detected and characterized by the use of the full-scan and dd-MS/MS using LC-HRMS, and this data can be useful for providing metabolite information for the interpretation of mass spectra of anabolic bolasterone analogues for doping screening tests.

The Power of Keratinous Matrices (Head Hair, Body Hair and Nail Clippings) Analysis in a Case of Death Involving Anabolic Agents.

A 29-year-old man with no previous medical history was found dead at home. Anabolic products (tablets and oily solutions) and syringes were found at the scene. The man was known to train regularly at a fitness club and to use anabolic drugs. Following an unremarkable autopsy with normal histology, toxicological analyses were requested by the local prosecutor to provide further information. Blood, head hair (5 cm, black), body hair (axillary and leg) and toe and finger nail clippings were submitted to liquid and gas chromatography coupled to tandem mass spectrometry (LC and GC-MS-MS) methods to test for anabolic steroids. Blood tested positive for testosterone (4 ng/mL), boldenone (26 ng/mL), stanozolol (3 ng/mL) and trenbolone (<1 ng/mL). Segmental head hair tests (2 × 2.5 cm) revealed a repeated consumption of testosterone (65-72 pg/mg), testosterone propionate (930-691 pg/mg), testosterone isocaproate (79 pg/mg to <5 pg/mg), nandrolone decanoate (202-64 pg/mg), boldenone (16 pg/mg), stanozolol (575-670 pg/mg), trenbolone (4 pg/mg-not detected), drostanolone (112-30 pg/mg), drostanolone enanthate (26-5 pg/mg) and drostanolone propionate (15-4 pg/mg). In addition to the substances identified in head hair, testosterone decanoate, testosterone cypionate and nandrolone were identified in both body hair and nails. The experts concluded that the manner of death can be listed as toxic due to massive repetitive use of anabolic steroids during the previous months. For anabolic agents, blood does not seem to be the best matrix to document a fatal intoxication. Indeed, these products are toxics when abused long term and are known to cause cardiac, hepatic and renal diseases. When compared to blood, hair and nails have a much larger window of detection. Therefore, keratinous matrices seem to be the best approach to test for anabolic steroids when a sudden death is observed in the context of possible abuse of steroids.

Novel nandrolone aptamer for rapid colorimetric detection of anabolic steroids.

The illicit use of anabolic androgenic steroids (AAS) as performance-enhancing drugs remains a global issue threatening not only the credibility of competitive sports but also public health due to the well-documented adverse effects they elicit. AAS abuse is not restricted only to professional sports, but also extends to recreational athletes and adolescents as well as in livestock production as growth-promoting agents. Testosterone and nandrolone are among the AAS most frequently exploited. Gas chromatography-mass spectrometry is the reference method for AAS detection, but it is strictly laboratory-based and cannot be performed on-site. The great potential of aptamers in bioanalytical applications and specifically for the development of simple analytical tools suitable for on-site analysis has been extensively documented. In this report, we describe the selection and identification of aptamers binding nandrolone, exhibiting affinity dissociation constants in the low nanomolar range. A label-free colorimetric assay based on gold nanoparticles was developed using one of these novel aptamers for the detection of nandrolone and/or its metabolites. The assay could be deployed for the rapid, on-site, facile and cost-effective screening of samples and provide qualitative visual results with a red to purple/blue color change being indicative of a positive result.

Stereoisomers in sports drug testing: Analytical strategies and applications.

Analytics employed in modern doping controls are designed to cover an extensive range of rather diverse classes of substances, all of which are banned in sport according to the list of prohibited substances and methods of doping, resulting from their potential to be performance-enhancing and/or harmful to health. Many of these bioactive substances or their metabolites are chiral, which are comprehensively characterized and, if appropriate analytical approaches are applied, can be clearly identified. In sports drug testing, the enantiomeric composition of relevant compounds is not considered in all instances, although differences of isomers concerning their biological activity have been established. To date, the separation of stereoisomers in doping controls is only applied for selected target compounds, but with the development of efficient chiral chromatographic stationary phases, the added value of information on e.g. racemic shifts during the metabolic biotransformation reactions of drugs has been recognized. The immense variability of the substance classes represents however a major challenge, especially because both 'classic' doping agents belonging to the category of lower molecular mass molecules (e.g. stimulants, ß2-agonists, betablockers, corticoids, etc.) as well as larger molecules from the category of peptides and proteins necessitate consideration. In the present (mini)review, the current status of analytical techniques in the field of doping control analysis of stereoisomers is highlighted and critically reviewed.

Development of a method for simultaneous screening of four natural-derived steroids and their analogues used as dietary supplements via liquid chromatography-quadrupole-time of flight mass spectrometry and liquid chromatography-tandem mass spectrometry.

Natural-derived steroids and their analogues are present in various plants and insects. To minimize the chance of missing a positive doping test and avoiding potentially serious health problems, adequate screening methods are necessary for the detection of a wide range of natural-derived steroids and their analogues in dietary supplements. In this study, an accurate and simple liquid-chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated to determine and quantify the natural-derived steroids and their analogues according to the International Conference on Harmonization of technical Requirements for Registration of Pharmaceuticals for Human Use guidelines. The validation results indicating excellent extraction efficiency and low matrix effects show that the LC-MS/MS method is reliable for the detection of natural-derived steroids and their analogues. In addition, we established the ion fragmentation of turkesterone and ion fragmentation of four natural-derived steroids and their analogues. The validated method was applied to 60 dietary supplements purchased online and in person from international vendors in 2020. Ecdysterone and 5α-hydroxylaxogenin were detected respectively in 3 and 14 of 60 dietary supplements. Especially, a high amount of 5α-hydroxylaxogenin, an FDA-unapproved ingredient, was detected in two of dietary supplements (44.4 and 32.3 mg/g). This component should be controlled since it may cause unexpected side effects if administered excessively. Thus, this method will be helpful for the continuous control and supervision of unlicensed dietary supplements containing natural-derived steroids and their analogues.

In vitro characterization of S-23 metabolites produced by human liver microsomes, and subsequent application to urine after a controlled oral administration.

The selective androgen receptor modulators are a recent class of anabolic agents, used to improve athletic performance. Among these molecules, there is (2 S)-N-(4-cyano-3-trifluoromethylphenyl)- 3-(3-fluoro-4-chlorophenoxyl)2-hydroxy-2-methyl-propanamide, commonly known as S-23. This molecule appeared very recently on the doping market. As a result, very few data are available in the literature, and nothing has been published about long-term effects of S-23. The authors focused on the detection of S-23 and its metabolites in human urine, following a single oral administration of approx. 8 mg to a volunteer, using standard ultra-performance liquid chromatography-triple quadrupole-mass spectrometry (UPLC-MS/MS), and ultra-performance liquid chromatography-quadrupole time of flight-mass spectrometry (UPLC-Q-TOF-MS). To the best of the authors knowledge, this seems to be the first study ever achieved on S-23. In vitro experiment was performed, using human liver microsomes, in order to investigate the potential CYP- and UGT-dependent S-23 metabolites. Four metabolites were produced, which were identified as hydroxy-S-23 (C18H12O4N2ClF4: m/z [M-H-] 431.0423); O-dephenylate-S-23 (C12H10O3N2F3: m/z [M-H-] 287.0647); S-23-glucuronide (C24H20O9N2ClF4: m/z [M-H-] 591.0794) and hydroxy-S-23-glucuronide (C24H20O10N2ClF4: m/z [M-H-] 607.0743). After consumption of S-23, the parent drug was detectable in hydrolyzed urine from 2 h post administration up to 28 days, with concentrations ranging between 0.5 and 93 ng/mL. In the urine, only one of the four metabolites identified in vitro was detected, hydroxy-S-23. This metabolite was detected up to 28 days. It does not seem to increase the window of detection of S-23 as the ratio between hydroxy-S-23 and the parent drug was always lower than 1. Another metabolite, dihydroxy-S-23, not identified in vitro, was identified in the urine of the volunteer. Hair sample, collected one month after the consumption of a single tablet, was negative for S-23 and hydroxy-S-23, with a LOQ at 0.1 pg/mg.

Simultaneous detection of 93 anabolic androgenic steroids in dietary supplements using gas chromatography tandem mass spectrometry.

In recent years, anabolic androgenic steroids (AASs) have been frequently detected as undeclared ingredients in dietary supplements, where the adverse analytical findings (AAFs) were obtained from analysis of athletes' urine samples after ingestion. In our present study, a GC-MS/MS method for simultaneous detection of 93 anabolic steroids was developed. The chromatographic and mass spectrometric conditions were optimized, and selective reaction monitoring (SRM) mode was adopted to obtain the necessary sensitivity. The whole sample analysis process was completed within 23 min, and the limit of detection (LOD) was 0.5-4 ng.g-1 for solid samples and 0.1-0.8 ng.mL-1 for liquid samples. This method was verified according to World Anti-Doping Agency (WADA) regulations. In addition, the method was found to be specific, accurate. The developed method was then applied to a routine analysis of more than 300 liquid and solid dietary supplements, and one testosterone-positive sample was found. Three suspected drugs, (4-hydroxyandrostenedione, DHEA, and 6-Br androstenedione) were found in three dietary supplements obtained from the Internet through the pretreatment method of this study. This study provides a high-throughput method for screening and monitoring the ingredients of supplements and their subsequent harm to public health.

Androgens, sports, and detection strategies for anabolic drug use.

For decades, anabolic androgenic agents have represented the substance class most frequently observed in doping control samples. They comprise synthetic and pseudoendogenous anabolic androgenic steroids and other, mostly non-steroidal compounds with (presumed) positive effects on muscle mass and function. While exogenous substances can easily be detected by gas/liquid chromatography and mass spectrometry, significantly more complex methodologies including the longitudinal monitoring of individual urinary steroid concentrations/ratios and isotope ratio mass spectrometry are required to provide evidence for the exogenous administration of endogenous compounds. This narrative review summarizes the efforts made within the last 5 years to further improve the detection of anabolic agents in doping control samples. Different approaches such as the identification of novel metabolites and biomarkers, the acquisition of complementary mass spectrometric data, and the development of new analytical strategies were employed to increase method sensitivity and retrospectivity while simultaneously reducing method complexity to facilitate a higher and faster sample throughput.

Simplified screening approach of anabolic steroid esters using a compact atmospheric solid analysis probe mass spectrometric system.

Due to the absence of chromatographic separation, ambient ionization mass spectrometry had the potential to improve the throughput of control laboratories in the last decades and will soon be an excellent approach for on-site use as well. In this study, an atmospheric solids analysis probe (ASAP) with a single quadrupole mass analyzer has been evaluated to identify anabolic steroid esters rapidly. Sample introduction, applied scan time, and probe temperature were optimized for sensitivity. The in-source fragmentations of seventeen selected steroid esters, commonly found in illicit samples, were determined by applying different cone voltages (12, 20, 30, and 40 V). A spectral library was created for these steroid esters based on the four stages of in-source fragmentation spectra. The applicability of this method was demonstrated for the rapid identification of steroid esters in oily injection solutions, providing test results in less than 2 min.

In vitro and in vivo metabolism of the anabolic-androgenic steroid oxandrolone in the horse.

Oxandrolone is an anabolic-androgenic steroid with favourable anabolic to androgenic ratio, making it an effective anabolic agent with less androgenic side effects. Although its metabolism has been studied in humans, its phase I and II metabolism has not been previously reported in the horse. The purpose of this study was to investigate the in vitro metabolism of oxandrolone (using both equine liver microsomes and S9) and in vivo metabolism following oral administration (three daily doses of 50 mg of oxandrolone to a single Thoroughbred horse), using both gas and liquid chromatography-mass spectrometry techniques. The in vitro phase I transformations observed included 16-hydroxylated (two epimers), 17-methyl-hydroxylated and 16-keto metabolites. In addition to parent oxandrolone and these hydroxylated metabolites, the 17-epimer and a 17,17-dimethyl-18-norandrost-13-ene analogue were detected in biological samples following the administration. 16-keto-oxandrolone was only observed in urine. The 16- and 17-methyl-hydroxylated oxandrolone metabolites were predominantly excreted as sulfate conjugates in urine, whereas parent oxandrolone, its epimer and 17,17-dimethyl-18-norandrost-13-ene derivative were found predominantly in the unconjugated urine fraction. The most abundant analyte detected in both plasma and urine was parent oxandrolone. However, the longest detection period using the developed analytical method was provided by 17-hydroxymethyl-oxandrolone in both matrices. The results of this study provided knowledge of how best to detect the use of oxandrolone in regulatory samples.