S-4 Andarine SARM Guide: Research, Uses and Cycle Information

S-4, Andarine and GTx-007 are names used for the same first-generation investigational selective androgen receptor modulator. Most publicly available S-4 research is preclinical and focuses on androgen-receptor activity in muscle, bone and other androgen-responsive tissues.

What Is S-4 Andarine?

S-4 is a nonsteroidal selective androgen receptor modulator, commonly abbreviated as a SARM. Andarine is its familiar market name, while GTx-007 is another development identifier associated with the same compound.

S-4 was one of the earlier compounds used to investigate whether androgen-receptor activity could be directed more strongly toward muscle and bone than toward tissues such as the prostate.

It remains investigational and has not been approved as a general muscle-building, cutting or athletic-performance medicine.

How Does S-4 Work?

S-4 binds to and activates androgen receptors. These receptors influence muscle, bone, reproductive tissue and other androgen-responsive systems.

Early pharmacology research found that S-4 produced tissue-selective anabolic activity in experimental models. Its anabolic activity in muscle-related measurements was stronger than its androgenic activity in tissues such as the prostate.

The word selective does not mean that S-4 acts only in muscle or that effects elsewhere are impossible.

Why S-4 Is Considered a First-Generation SARM

S-4 was among the first nonsteroidal compounds used to demonstrate that androgen-receptor activity could differ between tissues.

Its early development helped establish the scientific basis for later SARMs such as Ostarine, LGD-4033 and RAD-140.

Newer compounds later received more extensive human research, while most of the publicly available S-4 evidence remained focused on laboratory and animal models.

Preclinical Research on Muscle Strength

A controlled study evaluated S-4 in androgen-deficient male rats. Researchers examined skeletal-muscle strength, muscle mass, body composition and androgen-responsive tissues.

S-4 restored soleus-muscle strength and increased lean body mass in the experimental animals. The researchers also reported anabolic activity in muscle with weaker stimulation of prostate tissue than a full androgen response.

These results helped generate interest in Andarine for muscle and physical-function research. They were animal findings and cannot establish a guaranteed strength or muscle-building result in humans.

S-4 and Lean Body Mass Research

Preclinical studies reported increases or preservation of lean body mass in models involving androgen deprivation and reduced bone density.

Lean body mass includes muscle, water, connective tissue and other non-fat components. It should not automatically be interpreted as an equal increase in visible contractile muscle.

There is no equivalent published placebo-controlled bodybuilding study showing a specific lean-mass increase from S-4 in healthy recreational users.

S-4 and Bone Research

Additional research examined S-4 in female rats with reduced bone density following removal of the ovaries.

The researchers reported that S-4 maintained whole-body bone mineral density, cortical bone content and bone strength while also supporting skeletal-muscle performance.

These findings contributed to early interest in SARMs as possible treatments for conditions involving both muscle and bone loss.

The results remain preclinical and do not establish S-4 as an approved treatment for osteoporosis or fractures.

What Human Research Exists for Andarine?

S-4 reportedly entered early clinical development, but detailed peer-reviewed human efficacy results are not widely available.

Unlike Ostarine and LGD-4033, S-4 does not have a well-established published human trial showing quantified changes in lean body mass, strength or physical function.

Claims about Andarine cycles in healthy users therefore rely mainly on preclinical research and non-medical community experience rather than controlled human performance studies.

Why S-4 Is Discussed for Cutting

Andarine is commonly associated with cutting because its preclinical research involved lean body mass, muscle strength and tissue-selective androgen-receptor activity.

These findings led to performance-market discussions about retaining lean tissue while reducing calorie intake.

S-4 should not be described as a direct fat-burning compound. Published research has not established that it independently causes a specific reduction in body fat in healthy people.

Body-fat changes remain strongly influenced by total calorie intake, nutrition, activity and training.

S-4 and Muscle Hardness Claims

Terms such as dry muscle, hardness and definition are frequently used in non-medical Andarine discussions.

These descriptions are subjective and are not standardized outcomes used in controlled S-4 research.

Changes in appearance can also be influenced by body-fat level, hydration, carbohydrate intake, training and lighting, so these terms should not be presented as guaranteed product effects.

Common S-4 Cycle Discussions

Online SARM communities commonly discuss Andarine cycles lasting approximately six to eight weeks, with daily amounts frequently discussed in the 25–50 mg range.

These are non-medical community patterns rather than clinically validated protocols. Publicly available research does not establish an approved bodybuilding amount or cycle duration for S-4.

Greater exposure should not automatically be assumed to produce proportionally greater muscle, strength or body-composition results.

S-4 and Changes in Vision

Changes in visual adaptation, colour perception and low-light vision have been reported in connection with Andarine.

The publicly available peer-reviewed human evidence is limited, so the frequency, exposure relationship and individual susceptibility are not well established.

Visual symptoms should not be dismissed as a harmless sign that the compound is working. Changes in eyesight can affect driving, training and other activities that require accurate visual perception.

Does S-4 Require PCT?

S-4 activates androgen receptors and may affect normal hormonal signalling. The degree of suppression and recovery may vary according to the amount used, duration, previous exposure, additional compounds and individual hormone levels.

A shorter cycle should not automatically be treated as non-suppressive. Cycle length alone cannot determine whether post-cycle support may be appropriate.

Blood testing before and after a cycle provides more useful information than relying only on symptoms or applying the same PCT plan automatically.

Available options can be compared in the SARM PCT and Post-Cycle Support category. Enclomiphene, Clomid, Nolvadex, Arimidex and HCG work through different mechanisms and should not be treated as interchangeable products.

S-4 Compared With Ostarine

S-4 and Ostarine are both genuine selective androgen receptor modulators, but their research histories differ.

Ostarine MK-2866 has controlled human studies involving lean body mass and physical function. Publicly available S-4 evidence is weighted much more heavily toward animal research.

The Sarms Thailand S-4 product contains 25 mg per ml, which is the same labeled concentration as the Ostarine product. Identical concentration does not mean that the two compounds have identical potency, effects or research profiles.

S-4 Compared With LGD-4033

LGD-4033 Ligandrol has a published placebo-controlled study in healthy men that measured lean body mass, hormones and lipid markers over 21 days.

S-4 has extensive early preclinical pharmacology but much less publicly available human evidence.

Claims that one is automatically better for cutting or bulking are not established through direct comparative human trials.

S-4 Compared With RAD-140

S-4 and RAD-140 both activate androgen receptors but are different chemical compounds.

RAD-140 Testolone has published human research from an oncology trial, while S-4 research is primarily preclinical.

Neither compound has a controlled human bodybuilding trial establishing a guaranteed increase in muscle, strength or fat loss in healthy users.

S-4 in SARM Stacks

S-4 appears in pre-built combinations including the Bulking SARM Stack and CrossFit SARM Stack.

Some packages also contain LGD-4033, Ostarine or MK-677. MK-677 is not a SARM and acts through the ghrelin receptor rather than the androgen receptor.

Combining several compounds creates a more complex cycle than using S-4 alone. Each ingredient should be reviewed according to its own mechanism, evidence base and monitoring considerations.

Current combinations can be compared in the SARM Stacks in Thailand category.

S-4 Research Status

S-4 remains an investigational selective androgen receptor modulator. Its publicly available evidence includes pharmacology, muscle, body-composition and bone studies conducted primarily in experimental animals.

It has not been approved as a general bodybuilding, cutting or athletic-performance medicine.

S-4 and Andarine are prohibited under the World Anti-Doping Agency Prohibited List. Athletes subject to testing should avoid products containing S-4, Andarine or GTx-007.

Frequently Asked Questions

Are S-4, Andarine and GTx-007 the same compound?

Yes. S-4 is the research code, Andarine is the familiar market name and GTx-007 is another development identifier associated with the same substance.

Is Andarine a real SARM?

Yes. S-4 Andarine is a nonsteroidal selective androgen receptor modulator that activates the androgen receptor.

Has S-4 been studied in humans?

S-4 entered early clinical development, but detailed peer-reviewed human efficacy results are not widely available. Most published evidence involving muscle, bone and body composition comes from animal research.

Has S-4 been proven to burn fat?

No controlled human study has established a specific fat-loss result from Andarine. Its cutting reputation is based mainly on preclinical findings and non-medical community use.

How much S-4 is in 1 ml?

In a liquid containing 25 mg per ml, one full millilitre contains 25 mg of S-4 Andarine.

Can Andarine affect vision?

Changes in colour perception, visual adaptation and low-light vision have been reported in connection with Andarine. The full frequency and exposure relationship are not established through detailed published human trials.

Does every S-4 cycle require PCT?

No single answer applies to every cycle. Exposure, duration, other compounds and individual hormonal response all matter. Relevant blood testing provides clearer information than cycle length alone.

S-4 Andarine Research Sources

• Early pharmacodynamics of S-4 and tissue-selective SARM activity
• S-4 research involving muscle strength, lean body mass and androgen-responsive tissues
• S-4 research involving body composition, bone density and bone strength
• NIH LiverTox overview of selective androgen receptor modulators
• PubChem information for Andarine, S-4 and GTx-007
• Official sport-integrity information concerning Andarine and visual effects
• World Anti-Doping Agency Prohibited List