SARMs vs Anabolic Steroids: What the Evidence Actually Shows

What Are Anabolic-Androgenic Steroids?

Anabolic-androgenic steroids are synthetic derivatives of testosterone designed to amplify its muscle-building (anabolic) effects while retaining, to varying degrees, its masculinizing (androgenic) effects. The FDA has approved a small number for specific medical indications: oxandrolone for muscle wasting, nandrolone decanoate for anemia of renal disease, and testosterone itself for hypogonadism. Outside those narrow uses, supraphysiologic AAS dosing is a Schedule III controlled substance under the Anabolic Steroid Control Act of 1990 [1].

AAS work by entering cells, binding the androgen receptor (AR), and translocating the ligand-receptor complex to the nucleus, where it drives transcription of genes governing protein synthesis, nitrogen retention, and red blood cell production. Because the AR is expressed in skeletal muscle, prostate, liver, skin, hair follicles, and the central nervous system, classical AAS produce systemic effects across all these tissues simultaneously [2].

Supraphysiologic testosterone doses used in research (600 mg/week) increased fat-free mass by 6.1 kg over 10 weeks compared with 0.8 kg in the placebo group, a difference with P<0.001 [3]. That gain comes with measurable costs: the same trial documented suppression of serum luteinizing hormone (LH) to near-zero in every participant receiving 600 mg/week.

Common clinical AAS include testosterone enanthate, testosterone cypionate, nandrolone decanoate (Deca-Durabolin), stanozolol (Winstrol), and oxandrolone (Anavar). Street-use doses typically run 5 to 10 times the therapeutic range [4].

What Are SARMs?

SARMs are a class of nonsteroidal compounds engineered to bind the androgen receptor with high affinity while producing a different conformational change than testosterone. That altered receptor shape recruits different coactivator proteins in different tissues, theoretically producing anabolic signaling in muscle and bone without proportional androgenic signaling in the prostate and skin [5].

None are FDA-approved. The FDA issued a public safety warning in 2017 and again in 2023 noting that SARMs have been linked to "life-threatening reactions including liver toxicity" and warning consumers that products sold as SARMs are often adulterated or mislabeled [6]. The World Anti-Doping Agency (WADA) has prohibited all SARMs since 2008 [7].

The most studied compounds include ostarine (MK-2866, enobosarm), LGD-4033 (ligandrol), RAD-140 (testolone), andarine (S-4), and YK-11. Each has reached Phase I or Phase II trials, but none has cleared Phase III. The furthest along, enobosarm, failed its co-primary endpoint in a key Phase III muscle-wasting trial in 2013, although it did show statistically significant lean mass gains [8].

Mechanism: Where SARMs and AAS Actually Differ

Both classes activate the same receptor. The difference is downstream. Classical AAS, once bound to the AR, produce full agonism across virtually all androgen-responsive tissues. Oral 17-alpha-alkylated AAS (stanozolol, oxandrolone, methyltestosterone) additionally undergo first-pass hepatic metabolism that stresses cytochrome P450 pathways and elevates liver enzymes [9].

SARMs are designed as partial or tissue-selective agonists. In preclinical models, ostarine produced anabolic effects in muscle at doses that caused minimal prostate weight gain. A Phase II trial in 120 healthy elderly adults found that 3 mg/day of ostarine for 12 weeks increased lean body mass by 1.4 kg versus 0.02 kg for placebo (P<0.001), with no statistically significant change in prostate-specific antigen (PSA) [10].

That selectivity is real but incomplete. RAD-140, for instance, still suppresses LH and FSH measurably at doses used by recreational users (10 to 20 mg/day), and case reports of severe drug-induced liver injury (DILI) from RAD-140 have appeared in peer-reviewed hepatology literature [11].

Efficacy Comparison: Muscle and Strength Gains

AAS produce larger absolute gains than any SARM studied so far. This is not surprising. Full AR agonism in muscle, combined with supraphysiologic androgen levels, drives protein synthesis more aggressively than a tissue-selective partial agonist at investigational doses.

The 600-mg testosterone study cited above showed 6.1 kg of lean mass in 10 weeks [3]. Ostarine at 3 mg/day produced 1.4 kg over 12 weeks [10]. LGD-4033 at 1 mg/day (the highest dose studied in Phase I) added approximately 1.2 kg of lean mass over 21 days compared with placebo, with a dose-dependent suppression of total testosterone at all doses tested [12].

Oxandrolone (Anavar), the mildest well-studied oral AAS, produced mean lean mass gains of 2.8 kg over 12 weeks at 20 mg/day in a controlled trial of HIV-associated wasting [13]. Compared with ostarine at similar duration, oxandrolone produced roughly double the lean mass, but also carried significantly greater HDL suppression (HDL fell 30% vs. approximately 10% with ostarine).

For strength, the picture is similar. A meta-analysis of 9 AAS trials (N=281) found a weighted mean increase in bench-press strength of 9.4 kg above placebo-treated controls [14]. No comparable SARM meta-analysis exists because the trial database is too small, though LGD-4033 Phase I data showed stair-climb power increase at all active doses.

The HealthRX clinical team uses the following decision framework when patients ask about these compounds. First, establish whether any FDA-approved indication applies (e.g., hypogonadism for testosterone, wasting for oxandrolone). Second, quantify cardiovascular and hepatic baseline risk using a lipid panel, liver function tests, and hematocrit. Third, if a patient is researching SARMs independently, counsel that no human safety data extends beyond 12 to 24 weeks, that suppression of the HPG axis is dose-dependent and documented, and that the risk-benefit calculation differs substantially from that for prescription AAS under medical supervision.

Side-Effect Profiles: A Tissue-by-Tissue Breakdown

Cardiovascular

Both classes worsen lipid profiles. Oral AAS produce the most severe changes. Stanozolol at 6 mg/day reduced HDL cholesterol by 33% in a controlled crossover study [15]. Testosterone enanthate 300 mg/week reduced HDL by approximately 13% over 20 weeks in a controlled study of healthy men [16]. LGD-4033 at 1 mg/day reduced HDL by 40% at day 21 in Phase I data [12]. That HDL reduction from a low-dose investigational SARM exceeding the reduction seen with moderate-dose testosterone is a finding that deserves careful attention.

Left ventricular hypertrophy is well-documented with long-term AAS use. Echocardiographic studies in AAS-using bodybuilders show interventricular septal thickness 15 to 20% greater than matched non-using controls, with reduced diastolic function [17]. Equivalent long-term cardiac data for SARMs do not exist because no one has been studied for more than two years.

Liver

17-alpha-alkylated oral AAS carry the highest hepatotoxicity risk of any androgenic compound. Peliosis hepatis, cholestatic jaundice, and hepatocellular carcinoma have all been reported [9]. Injectable testosterone esters are not 17-alpha-alkylated and carry far lower direct hepatotoxicity risk, though cholestasis can still occur at supraphysiologic doses.

SARMs are not 17-alpha-alkylated, but multiple published case reports document acute DILI with RAD-140 and LGD-4033, some requiring hospitalization and one requiring liver transplant evaluation [11]. The FDA's adverse event reporting system (FAERS) contains dozens of hepatotoxicity reports tied to SARM-containing supplements [6].

HPG Axis Suppression

This is the area where SARMs offer the least claimed advantage. LGD-4033 at 1 mg/day suppressed total testosterone from a median of 619 ng/dL to 289 ng/dL at day 21 [12]. Recovery to baseline took 56 days after cessation. Ostarine at higher doses (3 mg/day) also produces measurable suppression, though less severe than LGD-4033 in head-to-head Phase I comparisons.

AAS suppression is complete and rapid. Testosterone enanthate 600 mg/week drives LH and FSH to near-zero within two weeks. Recovery of the HPG axis after a 10-week AAS cycle typically requires 3 to 6 months without pharmacologic intervention, and in some cases, recovery is incomplete [18].

Androgenic Effects (Acne, Hair Loss, Virilization)

Classical AAS are converted by 5-alpha reductase to dihydrotestosterone (DHT), a potent androgen that drives scalp hair loss in genetically susceptible individuals and acne in most users at supraphysiologic doses. Nandrolone is less prone to 5-alpha reduction than testosterone; this is why it is sometimes described as "milder" on hair [2].

SARMs are not substrates for 5-alpha reductase and do not aromatize to estrogen. Acne and hair-loss risk is lower in the available trial data, though RAD-140 case reports do include androgenic side effects [11]. Women face virilization risk with AAS at any supraphysiologic dose. SARM risk in women is less characterized, but ostarine at 3 mg/day caused no virilization in post-menopausal female subjects in Phase II data [10].

Ostarine vs. LGD-4033: The Most Common SARM Comparison

Ostarine (MK-2866) and LGD-4033 (ligandrol) are the two SARMs with the most human clinical trial data, though "most data" here still means only Phase I and Phase II.

Ostarine is the milder compound. Phase II data show 1.4 kg lean mass gain at 3 mg/day over 12 weeks with minimal PSA change and no liver signal in the trial population [10]. Recreational users typically take 10 to 25 mg/day, doses for which no controlled human safety data exist.

LGD-4033 is significantly more potent at binding the androgen receptor. Phase I showed 1.2 kg lean mass gain at only 1 mg/day over 21 days, with dose-dependent HPG suppression at every dose tested and a 40% HDL drop [12]. At the 10 to 20 mg doses common in bodybuilding communities, these effects are expected to be substantially more pronounced.

For someone weighing a choice between the two for body-composition purposes: ostarine produces smaller gains with a modestly better safety signal in trial data. LGD-4033 produces faster and larger gains alongside more pronounced suppression and lipid changes. Neither is safe at recreational doses by any standard the FDA or EMA would recognize [6].

Anavar (Oxandrolone) vs. Ostarine: The Closest Comparison

Oxandrolone is often positioned as the "mildest" oral AAS and is sometimes compared with ostarine by users seeking a lower-risk option. Both are oral, both are studied in muscle-wasting populations, and both produce moderate lean mass gains.

At 20 mg/day for 12 weeks, oxandrolone produced 2.8 kg lean mass in HIV-wasting patients [13]. Ostarine at 3 mg/day produced 1.4 kg over the same duration [10]. Oxandrolone doubles the gain but carries 17-alpha-alkylation hepatotoxicity risk, requires Schedule III prescription status, and suppresses the HPG axis more than ostarine at comparable therapeutic doses.

Ostarine's advantage over oxandrolone is a cleaner liver-safety profile in trial data and lower androgenic side-effect burden. Oxandrolone's advantage is the larger anabolic effect and 40-plus years of clinical use data, including documented recovery of lean mass in burn patients, Turner syndrome, and short bowel syndrome [19].

The Endocrine Society's 2010 testosterone therapy guideline states: "We recommend against the use of testosterone therapy in men with prostate or breast cancer and in those in whom the risks outweigh the benefits." The same principle of individualized risk-benefit analysis applies to any androgenic compound, including SARMs, where risks are less well characterized [20].

Clenbuterol vs. Cardarine: A Separate but Related Comparison

Clenbuterol and cardarine (GW501516) are not SARMs or AAS. Both are used by bodybuilders for fat loss and are often grouped in the same conversations.

Clenbuterol is a beta-2 adrenergic agonist approved in some countries as a bronchodilator for asthma but not approved for human use in the United States. It increases metabolic rate and thermogenesis. Case series document cardiac arrhythmias, hypokalemia, and tachycardia in recreational users [21]. The FDA has issued multiple import alerts for clenbuterol-containing products [22].

Cardarine (GW501516) activates the peroxisome proliferator-activated receptor delta (PPARdelta). It is not an androgen receptor ligand at all, which is why calling it a SARM is technically incorrect. Preclinical studies showed dramatic improvements in endurance and fat oxidation. Those same preclinical studies also showed dose-dependent multi-organ carcinogenesis in rats, which caused GlaxoSmithKline to terminate its development in 2007 [23]. The compound is banned by WADA and carries a carcinogenicity signal with no safety threshold established in humans.

Of the two compounds in this comparison, neither is appropriate for human performance use. Clenbuterol carries a documented cardiac risk. Cardarine carries a carcinogenicity signal serious enough that its developer stopped all trials [23].

Legality and Drug Testing

AAS are Schedule III controlled substances under federal law in the United States. Possession without a valid prescription is a federal crime. Distribution carries felony-level penalties [1].

SARMs occupy a grayer legal zone. They are not scheduled under the Controlled Substances Act as of early 2025, but the SARMs Control Act (proposed multiple times in Congress) would place them in Schedule III. The FDA considers SARMs unapproved drugs and has taken enforcement action against multiple supplement companies marketing them [6]. WADA prohibits them in all competitive sport [7].

Any competitive athlete should be aware that both classes are detectable with modern anti-doping methods. Testosterone and its synthetic derivatives are detected via gas chromatography-mass spectrometry and the carbon isotope ratio test. SARMs are detected via liquid chromatography-tandem mass spectrometry, and detection windows extend to several weeks post-dose depending on the compound and the dose [24].

Who Is Prescribed AAS Medically, and What Doses Apply?

FDA-approved indications for AAS include hypogonadism (testosterone), anemia associated with renal failure (nandrolone decanoate), and muscle wasting from HIV infection or surgery (oxandrolone). Testosterone replacement therapy for hypogonadism typically targets serum testosterone of 400 to 700 ng/dL, well within the physiologic range [20].

Bodybuilding and performance doses run 400 to 1 to 000 mg/week of testosterone equivalents, producing serum levels 5 to 10 times the upper limit of normal. The risk-benefit calculation at those doses is categorically different from medically supervised TRT.

No SARM has an approved medical indication. Any use is off-label or illegal, depending on how the product is obtained.

Key Risks Patients Often Underestimate

Polypharmacy stacking is common in AAS and SARM communities. Users frequently combine multiple compounds simultaneously, multiply individual side-effect risks in ways that are not studied, and self-administer post-cycle therapy (PCT) with clomiphene or tamoxifen to restart the HPG axis. A cross-sectional survey of 2,385 AAS users found that 56% used three or more compounds per cycle, and only 8% reported medical supervision [4].

Blood markers change faster than symptoms. HDL suppression from LGD-4033 reached statistical significance by day 21 [12], long before most users would feel any cardiac symptoms. Liver transaminases can spike within days of starting an oral 17-alpha-alkylated AAS. Baseline and on-cycle monitoring of a complete metabolic panel, CBC, and lipid panel is the minimum standard any clinician would apply to supervised use.

Long-term fertility impact is a genuine concern. A case series published in the Journal of Clinical Endocrinology and Metabolism documented azoospermia persisting 12 to 24 months after AAS cycle cessation in 24 of 41 men studied [18]. SARM-induced infertility data are sparse, but LGD-4033-mediated HPG suppression to below 300 ng/dL total testosterone for at least 56 days per cycle is not a trivial reproductive risk [12].