Andarine (S4)

Andarine (S4) is a SARM — a selective androgen receptor modulator (a lab-made molecule designed to act on the body’s testosterone-sensing system in a targeted way). It is a synthetic small molecule, not a peptide and not an anabolic steroid. You will often see it sold in fitness, biohacking, and “research chemical” circles as a muscle-building “safer steroid alternative.” But the real evidence behind it comes almost entirely from studies in rodents, and the single best-documented thing it does in people is a side effect — reversible vision changes — not a proven benefit.

What it is

Andarine (also called S-4, GTx-007 / GTX-007) belongs to a chemical family called arylpropionamides. It is taken by mouth, and it acts as a partial agonist of the androgen receptor (the cell switch that testosterone normally flips; “partial agonist” means it turns the switch only part of the way on).

What made it interesting in early research was tissue selectivity — the idea that it could act on some tissues more than others. In animal studies it behaved almost like a full “on” switch in muscle, but only a partial switch in the prostate. That is the whole pitch behind SARMs: muscle benefit without fully stimulating the prostate. And again, it is not a peptide.

The claims

In fitness and “research chemical” marketing, andarine is sold for lean muscle gain, fat loss, body recomposition, strength, and a “harder,” more vascular look — often as a “safer steroid alternative” or combined (“stacked”) with other SARMs. None of these performance or appearance claims are backed by finished human trials showing that andarine actually works.

What the evidence actually shows

• Animal studies: The strongest findings come from castrated rats. S-4 kept or restored the weight of the levator ani (an androgen-sensitive muscle) back toward normal, while only partly restoring prostate weight — showing the tissue-selective muscle effect described above (Yin/Gao et al., J Pharmacol Exp Ther 2003; Gao et al., Endocrinology 2004). It also helped protect bone in rodent models of osteoporosis (thinning, fragile bones).
• In people: Andarine only ever reached early Phase 1 testing (the first, small safety stage of human trials). There are no completed, published Phase 2 or Phase 3 trials (the larger studies that would actually test whether it works) showing benefit for muscle wasting or anything else.
• Discontinued: Development was stopped, reportedly because of vision problems seen in clinical studies — andarine’s signature reported side effect.

Bottom line on the evidence: there is essentially no solid record of benefit in humans, and the clearest human finding is a safety concern, not proof that it works.

Legal and regulatory status

• FDA: Andarine, and SARMs in general, are not FDA-approved for any use and are not legal dietary-supplement ingredients. The FDA has said SARMs sold as “supplements” are really unapproved drugs, has sent warning letters, and has put out consumer warnings (including one aimed at teens and young adults) flagging risks like liver injury, heart attack, stroke, and other serious harms. BSCG, a group that certifies supplements for athletes, also lists andarine as an illegal supplement ingredient.
• DEA: As of June 2026, SARMs (including andarine) are not federally scheduled controlled substances. Bills to add SARMs to Schedule III (the “SARMs Control Act,” for example S.2742 in the 115th Congress, 2018, and later re-introductions) have not become law. One important point: this is not the same as anabolic-steroid law. Oxandrolone is a true anabolic-androgenic steroid and a Schedule III controlled substance, and it should not be lumped in with SARMs.
• Anti-doping (WADA): All SARMs, andarine included, are banned at all times — both in and out of competition — under category S1.2, “Other Anabolic Agents.” For comparison: GW-501516 / cardarine works through a different target (it is a PPARδ agonist), and SR9009/SR9011 work through yet another (they are REV-ERB agonists). None of those are SARMs, even though they are often sold as if they were.

Safety

• Vision effects (specific to andarine): The most consistently reported effect in people is a temporary vision change — a yellowish tint to what you see, trouble adjusting to the dark or to night, and sensitivity to blue light and flashes. It appears to depend on the dose and to go away after stopping. The proposed explanation is that andarine interacts with androgen receptors in the retina (the light-sensing layer at the back of the eye), though that is an educated guess, not something firmly proven. This is the reported reason its clinical development was stopped.
• Testosterone suppression (the HPG axis — the brain-to-testes hormone loop): Because andarine switches on the androgen receptor, it — like SARMs as a group — is expected to lower the body’s own testosterone, LH, and FSH (hormones that control testosterone production) through negative feedback (the body sensing the outside signal and dialing back its own). This shutdown is a well-established effect across the SARM class.
• Cholesterol (HDL): SARMs as a group are linked to lower HDL cholesterol (the “good” cholesterol), something documented for oral SARMs such as ostarine/enobosarm. Andarine-specific human cholesterol data are limited.
• Liver injury (hepatotoxicity, meaning harm to the liver): Real-world SARM users have had drug-induced liver injury, including hospitalizations, and these cases are tracked in NIH LiverTox (a government database of liver-harming drugs). Most published cases involve other SARMs (ostarine, LGD-4033, RAD140); reports tied specifically to andarine are sparse, but the warning sign for the class is real.
• For contrast (a different compound): Development of GW-501516 was halted around 2007 after a long-term rodent study found tumors across several organ systems at chronic high doses. That cancer-causing finding applies to GW-501516, not andarine — there is no comparable finding for andarine.
• What we will not claim: There is no reliable evidence that andarine specifically causes permanent blindness or QT-interval prolongation (a heart-rhythm problem). Its reported vision effects are reversible.

This profile includes no dosing amounts, cycles, or protocols by design.

Bottom line

Andarine is a SARM whose tissue-selective, muscle-building effects have only been shown in animals. There are no completed human trials proving it works, it is not approved or legal as a supplement, and it is banned at all times in sport. The clearest piece of human data is a side effect — reversible vision disturbance — and that is why its development was abandoned. Concerns that run across the whole SARM class (testosterone suppression, lower HDL cholesterol, and liver injury) add more reason for caution.

Evidence grade: 3/10 · Animal only.

Sources

• He Y, Yin D, Perera M, et al. Novel nonsteroidal ligands with high binding affinity and potent functional activity for the androgen receptor. Eur J Med Chem. 2002. PMID 12161060
• Yin D, Gao W, Kearbey JD, et al. Pharmacodynamics of selective androgen receptor modulators. J Pharmacol Exp Ther. 2003. PMID 12604714
• Gao W, Kearbey JD, Nair VA, et al. Comparison of the pharmacological effects of a novel selective androgen receptor modulator, the 5α-reductase inhibitor finasteride, and the antiandrogen hydroxyflutamide in intact rats. Endocrinology. 2004. PMID 15308613
• FDA — FDA Warns of Use of Selective Androgen Receptor Modulators (SARMs) Among Teens, Young Adults
• FDA — Certain bodybuilding products put consumers at risk for heart attack, stroke, serious liver damage and more
• WADA — The Prohibited List
• USADA — Selective Androgen Receptor Modulators (SARMs): Prohibited Class of Anabolic Agents
• USADA — What Should Tested Athletes Know About GW1516?
• BSCG — Andarine: A Banned Substance in Sport and Illegal Dietary Supplement Ingredient
• Congress.gov — S.2742 SARMs Control Act of 2018 (not enacted)
• NIH LiverTox — Selective Androgen Receptor Modulators
• Khan S, Fackler J, Gilani A, Murphy S, Polintan L. Selective Androgen Receptor Modulator Induced Hepatotoxicity. Cureus. 2022;14(2):e22239. PMC8929477
• Wikipedia — GW501516 (contrast compound)
• Wikipedia — Andarine