Andarine (S4) Benefits: What the Research Actually Shows

Key takeaways

What Andarine (S4) Is and Why It Was Developed

Andarine, also known as S-4 or GTx-007, is a nonsteroidal selective androgen receptor modulator (SARM) developed by GTX, Inc. It was designed for the treatment of muscle wasting, osteoporosis, and benign prostatic hyperplasia, using the nonsteroidal antiandrogen bicalutamide as a chemical starting point.

The goal of this research program, like that of other SARMs, was to find a compound that would stimulate androgen receptors in muscle and bone the way testosterone does, while activating receptors in the prostate and other reproductive tissues less than testosterone or dihydrotestosterone (DHT). Development of andarine was ultimately discontinued in favor of a structurally related, more advanced compound from the same research program, enobosarm (ostarine, GTx-024, S-22).

What Animal Studies Show

Almost everything known about andarine's biological effects comes from rodent studies. The most frequently cited study characterized its effects in castrated male rats. As the researchers described it, they set out to test the compound's activity "in skeletal muscle, bone, and pituitary of castrated male rats," building on earlier work that had demonstrated "the partial agonist activity of a selective androgen receptor modulator (SARM) in the prostate." A chemical supplier summary of this line of research states that GTx-007 (andarine) "improves muscle strength and prevents bone loss in orchidectomized rats" and that, like other SARMs, it "produces anabolic effects in muscle and bone without androgenic effects."

A separate study examined andarine in ovariectomized rats, a model used to study accelerated bone loss after loss of gonadal hormone production. That study was conducted to examine bone and body composition effects "in an ovariectomy induced model of accelerated bone loss," using 120 female rats followed for 120 days of treatment with whole-body and lumbar bone density measured by DEXA scanning. The researchers reported that andarine treatment "maintained whole body and trabecular BMD, cortical content, and increased bone strength while decreasing body fat in these animals."

Taken together, these two rodent studies are the basis for essentially every claim that andarine builds muscle, protects bone, reduces fat, or spares the prostate. They are legitimate, peer-reviewed animal pharmacology studies, but they are animal studies. Rodent androgen receptor pharmacology does not reliably predict human outcomes, dosing, or safety, and no published research has confirmed that these effects translate to humans at any dose.

No Published Human Clinical Trial Data

Unlike ostarine, which went through multiple published Phase 1, 2, and 3 human trials for muscle wasting and other indications, andarine's clinical development did not produce any published human trial results. Independent secondary reviews of the compound's history consistently describe it as abandoned before reaching the point of published human data, with GTx redirecting its SARM development program toward ostarine instead. Some sources report that early-phase human testing may have occurred internally, but no peer-reviewed publication of human pharmacokinetic, efficacy, or safety data for andarine exists in the scientific literature.

This absence of human data is directly reflected in how consumer health references describe andarine. The WebMD ingredient monograph notes that people use andarine "to improve athletic performance and for conditions such as involuntary weight loss in people who are very ill (cachexia or wasting syndrome), osteoporosis, and prostate health, but there is no good scientific evidence to support these uses." In other words, the uses promoted online are extrapolated from rat studies, not demonstrated in people.

Reported Adverse Effects

The adverse effect most consistently associated with andarine, based on user reports and secondary clinical summaries rather than controlled human trials, is altered vision. Health information sources describe this as the compound's most recognizable adverse effect, "particularly a yellow tint and difficulty adjusting to darkness." This is generally attributed to andarine's activity at androgen receptors in ocular tissue, though the mechanism has not been characterized in controlled human studies, and it is not known how common, dose-dependent, or reversible this effect is in the general population of people using the compound.

Beyond vision changes, andarine belongs to a drug class the FDA has repeatedly warned about in connection with serious harm. In its consumer warnings on bodybuilding products containing SARMs, the FDA states that "life-threatening reactions, including liver injuries that required hospitalization, have occurred in people taking products containing SARMs," and that SARMs also have the potential to cause increased risk of heart attack or stroke, psychosis and hallucinations, sleep disturbances, sexual dysfunction, liver injury and acute liver failure, infertility, pregnancy miscarriage, and testicular shrinkage. A published review of suspected adverse event cases involving SARM use found that the FDA "has issued a warning letter about the health risks associated with the use of body-building products containing SARMs," citing risk of heart attack, stroke, and liver damage, and case reports have documented drug-induced liver injury, including jaundice and markedly elevated liver enzymes, in people using products marketed as SARMs.

Because andarine has not been studied in controlled human trials, there is no reliable human data isolating its individual risk profile from that of the broader SARM class, and no data on long-term safety at any dose.

Regulatory and Anti-Doping Status

Andarine is not approved for any medical use anywhere. The WebMD monograph states plainly that "andarine is an investigational drug that has not yet been approved by the US Food and Drug Administration (FDA)" and that "the FDA considers supplements containing andarine to be illegal." The FDA has issued warning letters to companies selling andarine and other SARMs as bodybuilding products, and it has announced recalls after products marketed as supplements were found to contain undeclared andarine and other unapproved substances.

Andarine is also prohibited in sport. The World Anti-Doping Agency has banned SARMs as a class since 2008, and both in- and out-of-competition testing can detect andarine and its metabolites. Athletes are generally held responsible for any prohibited substance found in their system regardless of whether a product's label discloses it, and there is no FDA-approved SARM available by prescription for a therapeutic use exemption.

What This Means for "Benefits" Claims

The muscle-sparing, bone-protective, and prostate-sparing effects reported for andarine are real findings from peer-reviewed rat studies, and it is accurate to describe them as promising preclinical pharmacology. It is not accurate to describe them as established human benefits. No controlled human trial data on andarine's efficacy for muscle growth, fat loss, bone density, or any other outcome have been published, and the compound has never been approved by any regulatory authority for any indication. The adverse effects associated with SARM use in general, including reported liver injury, cardiovascular risk, and hormonal suppression, combined with andarine's characteristic vision disturbances, mean that any personal use of andarine involves exposure to an unregulated, unapproved compound with an unverified purity, no established human dosing, and no confirmed long-term safety profile.

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