Methylstenbolone

Overview

Methylstenbolone (commonly sold as M-Sten or Ultradrol) is an anabolic-androgenic steroid (AAS) — specifically a 17α-methylated (C17-alkylated) oral derivative of dihydrotestosterone (DHT). That is the single most important fact about it: it is a steroid, not a SARM and not a peptide, even though it is routinely marketed and grouped online alongside "SARM" and "prohormone" products in a way that implies a mild, low-risk profile.

It is the opposite of mild. Methylstenbolone is a full designer anabolic steroid that was never developed, tested, or approved as a medicine. It was introduced only as an ingredient in unregulated "prohormone" supplements. Because it carries a 17α-alkyl group (the structural modification that lets an oral steroid survive first-pass liver metabolism), it belongs to the class of oral steroids with the highest documented risk of liver injury.

Chemistry and structure

Methylstenbolone is a synthetic steroid built on the dihydrotestosterone (DHT) skeleton with two added methyl groups: one at the 2-position and one at the 17α-position, plus a 1-ene (δ1) double bond. The 17α-methyl group is what makes it orally active — it resists hepatic first-pass metabolism — and it is also the structural feature responsible for the hepatotoxicity shared across C17-alkylated oral AAS.

It is closely related to other 17α-alkylated designer steroids marketed as "prohormones" (for example the methasterone/Superdrol family), which share the same oral-activity-plus-liver-toxicity trade-off.

Mechanism of action

Methylstenbolone acts as a systemic androgen — the mechanism of a classical anabolic-androgenic steroid, not the tissue-selective mechanism claimed for a SARM.

• Androgen receptor (AR) agonism. [Mechanistic] As a DHT-derived AAS, it binds and activates the androgen receptor systemically, driving both anabolic (muscle) and androgenic effects throughout the body. It is not tissue-selective the way a true SARM is designed to be.
• 17α-alkyl (C17-methyl) structure. [Human] The 17α-methyl group confers oral bioavailability by resisting first-pass hepatic metabolism — but this same modification is the structural cause of the cholestatic liver injury documented across C17-alkylated oral steroids.
• HPTA suppression. [Mechanistic] Exposure to an exogenous androgen suppresses the hypothalamic-pituitary-testicular axis (HPTA) via negative feedback, lowering the body's own LH, FSH, and testosterone — a class effect of exogenous AAS.

Research and evidence

There is essentially no legitimate human efficacy literature for methylstenbolone: it was never studied as a medicine, so there are no controlled trials of its anabolic effect, potency, or safety. The published human evidence that does exist is almost entirely case reports of harm, plus class-level pharmacology.

Identity and class

Methylstenbolone is described in PubChem (CID 252380) and reference sources as a 17α-methylated derivative of DHT, an orally active anabolic-androgenic steroid that was never introduced for medical use and was sold instead as a designer "prohormone" supplement — chemical formula C21H32O2, molecular weight 316.48 g/mol, CAS 6176-38-1. [Human] Its classification is steroid, not SARM and not peptide.

Documented human hepatotoxicity

A published case report (Agbenyefia, Arnold, Kirkpatrick, J Investig Med High Impact Case Rep, 2014; PMID 26425606) described a 26-year-old previously healthy man who developed severe cholestatic jaundice — peak bilirubin 45.9 mg/dL, ALT 269 IU/L, with a liver biopsy showing canalicular/hepatocellular cholestasis — after taking Super DMZ Rx 2.0 (10 mg methylstenbolone + 10 mg dymethazine per capsule) twice daily for 30 days, exactly per the label. He recovered roughly 10 weeks after stopping. [Human] The injury occurred at the manufacturer-recommended dose, not an overdose — a critical point for anyone who assumes a "supplement" dose is inherently safe.

A second independent human case report (Vargas KEA et al., Medwin MJCCS, 2018) documents severe hepatotoxicity associated with methylstenbolone (together with stanozolol), reinforcing that this is a repeatable class pattern, not a single anomaly. [Human]

Class-level liver toxicity

NIH LiverTox ("Androgenic Steroids," NCBI Bookshelf NBK548931) documents that C17-alkylated oral androgens as a class cause cholestatic liver injury, peliosis hepatis, and hepatic tumors. Injury is usually (but not always) reversible on discontinuation and can occasionally become fulminant. [Human] This is the class-level evidence for the mechanism driving methylstenbolone's hepatotoxicity.

Status and regulation

Methylstenbolone was never developed, tested, or approved for any human medical use by the FDA, EMA, or any other regulator. There is no established therapeutic dose, no safety-monitoring protocol, and no pharmacokinetic data (including no established half-life). It exists only as an unregulated designer steroid.

In the United States it is a Schedule III controlled anabolic steroid under the Designer Anabolic Steroid Control Act of 2014 (DASCA), which amended the Controlled Substances Act to add designer steroids like methylstenbolone to the statutory definition of "anabolic steroid." Manufacturing, distributing, or possessing it without authorization is a federal offense.

In sport, it is prohibited at all times under the WADA Prohibited List, class S1.1 (exogenous anabolic androgenic steroids) — the AAS category, distinct from the separate S1.2 category that covers SARMs.

Safety

Methylstenbolone's safety profile is that of a potent oral anabolic-androgenic steroid, compounded by the fact that it is obtained only as an unregulated, frequently mislabeled product.

Hepatotoxicity — the headline risk [Human]

As a 17α-alkylated oral AAS, methylstenbolone causes cholestatic hepatitis / drug-induced liver injury. A published human case documented severe cholestatic jaundice (bilirubin ~46 mg/dL) at the label-recommended dose, and a second case report links it to severe hepatotoxicity. Class effects for C17-alkylated oral steroids also include peliosis hepatis (blood-filled cavities in the liver) and hepatic tumors. This is the risk that most defines the compound.

Testosterone / HPTA suppression [Mechanistic]

Like all exogenous AAS, it suppresses the hypothalamic-pituitary-testicular axis, lowering endogenous LH/FSH and testosterone. This can produce hypogonadism, infertility, and testicular atrophy, which may require an extended recovery period after stopping.

Cardiovascular / lipid harm [Mechanistic]

Oral 17α-alkylated AAS characteristically suppress HDL ("good") cholesterol and raise LDL — an atherogenic shift associated with increased cardiovascular risk in steroid users.

Virilization [Mechanistic]

Androgenic effects can cause irreversible virilization in women (voice deepening, hirsutism, clitoromegaly) and androgen-related effects in men (e.g. hair loss, acne). It is contraindicated in pregnancy.

Mislabeling, adulteration, and contamination [Human]

Methylstenbolone frequently appears as an undeclared or misrepresented ingredient in products sold as "supplements," "prohormones," or "SARMs." An analytical study of products marketed as SARMs (Van Wagoner et al., JAMA, 2017; PMID 29183075) tested 44 products and found that only ~52% (23 of 44) contained any SARM at all, while many contained unapproved drugs or other, unlabeled substances and most were inaccurately dosed versus the label. Designer steroids are a known undeclared adulterant class in this market. The practical consequence: a label is not a reliable statement of contents or dose — you cannot know what you are actually taking.

Not an approved medicine [Human]

It was never developed, tested, or approved for human use. There is no established therapeutic dose, no safety monitoring, and no pharmacokinetic data, including no established half-life. It is sold only as an unregulated designer steroid.

Legal status

• United States. Methylstenbolone is a Schedule III controlled anabolic steroid under the Designer Anabolic Steroid Control Act of 2014. Manufacturing, distributing, or possessing it without authorization is a federal offense. It is not a lawful dietary supplement.
• Sport (WADA). Prohibited at all times as an exogenous anabolic androgenic steroid (S1.1). Note that WADA prohibition is about sport eligibility, a separate axis from criminal/controlled-substance status.
• Other jurisdictions. Legal treatment of anabolic steroids and designer steroids varies by country; many jurisdictions control AAS and/or restrict unapproved medicines. Rules on import, possession, and sale differ.

This entry is educational and does not constitute legal or medical advice. Verify the current status in your own jurisdiction.

How it compares

Methylstenbolone is regularly grouped with SARMs in online marketing, but it is not one. True SARMs (selective androgen receptor modulators) are non-steroidal compounds designed to activate the androgen receptor selectively in some tissues; methylstenbolone is a steroidal, systemic full androgen with the classic AAS toxicity profile.

To be clear: being "not a SARM" does not make SARMs safe. True SARMs such as Ostarine and Testolone are also unapproved and carry their own documented risks. The point of the comparison is only that methylstenbolone is a full anabolic steroid and should be understood as one, not as the "milder" thing its marketing implies.

Common misconceptions

• "It's a mild SARM." It is not a SARM at all — it is a 17α-alkylated oral anabolic-androgenic steroid. The "SARM" framing is marketing, not chemistry.
• "A prohormone/supplement is safer than a real steroid." Methylstenbolone is a real (designer) steroid, and it caused severe liver injury at the label dose in a published case. "Prohormone" branding does not change the pharmacology or the risk.
• "If it were dangerous it wouldn't be sold as a supplement." It is a Schedule III controlled substance in the US precisely because it is a designer anabolic steroid, and it has been found as an undeclared/mislabeled ingredient in products where the label cannot be trusted.
• "The dose on the label is safe because it's low." The published cholestatic jaundice case occurred at the manufacturer-recommended dose, not an overdose.
• "Liver risk is the only concern." It also suppresses natural testosterone, worsens cholesterol/cardiovascular markers, and can cause virilization — and it has no established half-life or safety data because it was never studied as a medicine.