Methyltestosterone metabolites: how the body breaks down the drug
Methyltestosterone was one of the first orally active androgens ever synthesised, and it remains a textbook example of how a single chemical modification changes the way a steroid moves through the body. This editorial overview explains what happens to the molecule after it is swallowed, which metabolites it forms, and why those breakdown products matter for liver health and for anti-doping laboratories.
What methyltestosterone is
Methyltestosterone is a synthetic derivative of testosterone, the principal male sex hormone. Structurally it is testosterone with a single methyl group (CH3) attached at the 17-alpha position of the steroid skeleton. That small addition has an outsized effect: it allows the molecule to pass through the digestive tract and the liver in a biologically active form, something that ordinary testosterone cannot do efficiently when taken by mouth.
The compound was introduced into medicine in the 1930s and 1940s and is historically significant as one of the earliest orally available anabolic-androgenic steroids. In modern UK practice it has been almost entirely superseded by safer options, and it is a controlled substance under the Misuse of Drugs Act when supplied without authorisation. Its continued relevance is largely pharmacological and forensic rather than therapeutic.
Understanding how the body handles methyltestosterone is useful for several reasons. It clarifies why orally active steroids tend to be harder on the liver, it illustrates the chemistry behind doping tests, and it helps explain certain contaminated-supplement scandals in which methyltestosterone or its relatives have been detected. None of this requires knowing how the drug might be used; the focus here is on metabolism as a biological process.
It is worth stating plainly that this article does not describe how to use methyltestosterone, in what amounts, or for what purpose. Those questions belong to a prescriber working within the law. What follows is an account of the molecule's fate once it is inside the body.
Why it survives the liver: 17-alpha-methylation
When any substance is absorbed from the gut, it travels first to the liver through the portal vein before reaching the general circulation. This is called first-pass metabolism, and it is the reason plain testosterone is almost useless orally: the liver inactivates most of it before it can act. The 17-alpha-methyl group blocks the enzymes that would normally oxidise the 17-beta-hydroxyl group, so a meaningful fraction of the dose survives the first pass and enters the bloodstream intact.
This is the same structural trick found in several other oral steroids, which is why the whole class is sometimes called "17-alpha-alkylated" compounds. The benefit is oral activity; the cost is that the liver must repeatedly process a molecule that resists normal clearance. That resistance is the mechanistic root of the hepatotoxicity associated with this group.
The methyl group does not make the steroid "stronger" in a simple sense. It changes pharmacokinetics — how the drug is absorbed, distributed, metabolised and eliminated — rather than fundamentally altering what the active molecule does at the receptor. The androgenic and anabolic signalling still depends on binding to the androgen receptor, just as it does for testosterone itself.
Because the alkyl group interferes with normal hydroxylation at carbon 17, the body is forced to break the molecule down through alternative routes. Those alternative routes generate the characteristic metabolites discussed below, and they are precisely what makes methyltestosterone traceable long after the parent compound has gone.
The main metabolic pathways
Metabolism of methyltestosterone follows two broad strategies that the body uses for most steroids: phase I reactions, which chemically modify the molecule (oxidation, reduction, hydroxylation), and phase II reactions, which attach a water-soluble "tag" such as a glucuronide or sulphate to make the metabolite easier to excrete in urine.
In phase I, enzymes act on the A-ring of the steroid and at various carbon positions to produce reduced and hydroxylated forms. A particularly important reaction is reduction of the 3-keto group and the double bond in the A-ring, which yields diol and triol metabolites. Another, discussed in detail below, is a rearrangement at carbon 17 that produces an epimer of the parent drug.
In phase II, the modified molecules are joined to glucuronic acid or sulphate. These conjugates are far more water-soluble than the parent steroid and are filtered by the kidneys into urine. For the forensic chemist this is good news: the conjugated metabolites can be collected, cleaved in the laboratory and measured with great sensitivity.
The relative importance of each pathway varies between individuals because of genetic differences in the enzymes involved, particularly the cytochrome P450 family and the UDP-glucuronosyltransferases. This is one reason detection windows differ from person to person, and why anti-doping science relies on measuring several metabolites rather than a single marker.
Key metabolites and what they tell us
The most characteristic breakdown product is 17-epimethyltestosterone (17-epimethyltestosterone), formed by inversion of the configuration at carbon 17. This epimer is essentially unique to the parent drug and serves as a signature. Alongside it, laboratories look for reduced A-ring metabolites such as the 5-beta and 5-alpha diols. The table below summarises the principal markers and their value in testing.
| Metabolite | Formation | Significance |
|---|---|---|
| Parent methyltestosterone | Unmetabolised fraction | Short detection window; confirms recent exposure |
| 17-epimethyltestosterone | Epimerisation at C17 | Characteristic long-term marker in urine |
| 5-beta diol metabolites | A-ring reduction | Extends detection window |
| Hydroxylated conjugates | P450 hydroxylation + conjugation | Water-soluble; measured after cleavage |
These metabolites are not merely academic curiosities. In contaminated-supplement cases, the detection of methyltestosterone metabolites in an athlete's urine has repeatedly revealed that an over-the-counter product was adulterated with a prohibited steroid. The characteristic epimer is what distinguishes deliberate or accidental exposure to this specific drug from other androgens.
From a clinical standpoint, the metabolite profile also underlines why orally active 17-alkylated steroids are flagged as hepatically demanding. The liver cannot clear the parent compound through its usual 17-oxidation route, so the molecule lingers and is processed through the slower, more laborious pathways shown above.
It is important not to over-interpret a metabolite list. The presence of a marker in urine confirms exposure; it does not by itself quantify how much was taken or over what period, which is why laboratories combine concentration data, ratios and population reference ranges when they interpret a result.
Detection, half-life and the liver
Methyltestosterone itself has a relatively short plasma half-life, typically cited in the region of a few hours, which is why the parent compound disappears from the blood quickly. The metabolites, however, can be detected in urine for considerably longer — days in many cases — because the conjugated forms are stored and excreted more gradually. This mismatch between a short-lived parent and longer-lived markers is central to anti-doping strategy.
The World Anti-Doping Agency prohibits androgenic-anabolic steroids at all times, and methyltestosterone is explicitly covered. UK Anti-Doping, which administers the code domestically, relies on accredited laboratories that screen for the epimer and the reduced metabolites described above. For an athlete, the practical message is that these substances are traceable long after any subjective effect has worn off.
On the health side, the liver deserves particular attention. Because 17-alkylation forces the hepatocytes to handle a resistant molecule, the class is associated with raised liver enzymes, cholestasis (impaired bile flow) and, in rare but documented cases, blood-filled cysts within the liver known as peliosis hepatis. These risks rise with higher exposure and longer duration, and they are a recurring theme across all oral 17-alkylated steroids.
Studies of steroid metabolism — notably the long programme of work by Schänzer and colleagues — mapped these pathways precisely so that laboratories could identify even trace exposure. That same research base informs clinical understanding of why the oral route and the liver are so tightly linked for this family of drugs.
Anyone with abnormal liver blood tests, jaundice, dark urine or right-sided abdominal discomfort should seek medical assessment promptly, regardless of the suspected cause. These are general warning signs that warrant investigation by a clinician.
Conclusions of the editorial team
Methyltestosterone is a historically important oral androgen whose defining feature — a methyl group at carbon 17 — explains almost everything about its behaviour in the body. That group lets the drug survive the liver, forces metabolism down alternative routes, and generates the characteristic metabolites that laboratories now use to detect it.
The same chemistry that makes the compound orally active also makes it hepatically demanding, which is why this whole class carries a reputation for liver strain. The metabolite most worth knowing, 17-epimethyltestosterone, is both a forensic signature and a reminder of how the liver struggles to clear alkylated steroids.
For readers interested in the wider picture, our related material on 17-alpha-alkylation and liver load, on how anti-doping laboratories read a urine sample, and on the metabolism of other oral steroids such as oxandrolone places this single molecule in its proper context.
References
- Schänzer W. Metabolism of anabolic androgenic steroids. Clin Chem. 1996;42(7):1001–1020.
- Kicman AT. Pharmacology of anabolic steroids. Br J Pharmacol. 2008;154(3):502–521.
- Geyer H, Parr MK, Mareck U, et al. Analysis of non-hormonal nutritional supplements for anabolic-androgenic steroids. Int J Sports Med. 2004;25(2):124–129.
- Handelsman DJ. Androgen physiology, pharmacology and abuse. In: Endotext. MDText.com; 2020.
- World Anti-Doping Agency. The 2024 Prohibited List, International Standard. Montreal: WADA; 2024.
- Pope HG Jr, Wood RI, Rogol A, et al. Adverse health consequences of performance-enhancing drugs: an Endocrine Society scientific statement. Endocr Rev. 2014;35(3):341–375.
