What is S-23

Well, Here is what we know about it so far.


SARMs are also known as “selective androgen receptor modulators”, are a new class of chemical that selectively agonize or antagonize (activate or deactivate) androgen receptor sites in the body.

GTx Incorporated was the original developer of S-23, GTx is also the creator of Ostarine (Mk-2866), one of the very first SARMs ever designed.

S-23 is one of the most potent SARMs produced.

The difference between anabolic steroids and SARMs is the difference in selectivity of androgen receptors. Most AAS (Anabolic Androgenic Steroids), are not very selective and agonize most androgen receptors, including the receptors in organs and sensitive tissue like the prostate. SARMs, however, were designed to be selective to only specific, targeted receptor sites. The favorable receptor sites to selectively target are primarily muscular tissue and androgen receptors in the bone.


The idea was to develop a more powerful SARM to combat issues such as muscle wasting and bone density diseases.

S-23 has the potential to be used to treat the effects of HIV/AIDS, which causes the body to lose muscle drastically, and bone density.

It may also one day be capable of treating osteoporosis, a disease that lowers bone density within the body.

There will need to be more research completed to be able to confirm these theories.


  • S-23 can bind to Androgen Receptors with a much higher affinity for receptor sites than previous Sarms.
  • S-23 has a greater anabolic to androgenic ratio than Testosterone.

S-23 increases lean muscle mass, as well as increased bone strength. Meaning you could see growth in the muscles without the addition of fat or water retention.

Selective tissue targeting is beneficial for obvious reasons; for instance, helping you produce more muscle mass without the side effects of classical anabolic steroids, which aren’t as selectively binding. Steroids always lead to muscle growth and fat and water retention due to the way they increase estrogen in the blood.

  • S-23 causes suppression of spermatogenesis. Spermatogenesis resumed with the cessation of usage.

S-23 also has the potential to be used as a male contraceptive since it drastically reduces a man’s sperm count, but only for the time that he is on it. Luteinizing hormone and Follicle Stimulating Hormone (LH and FSH, respectively) are suppressed by S-23. These two hormones stimulate spermatogenesis, which is the production of sperm in the testes.

As S-23 suppresses these hormones, the user’s Testosterone production slows down, and the sperm count lowers. Scientists think it may be possible that S-23 could become an option for the “male contraceptive pill” because it does not have lasting adverse effects on reproduction and can be taken for extended periods.


  • Studies showed that animals treated with Estradiol Benzo and S-23 were leaner than intact controls with lower average body weight, and significantly less percentage of fat mass.
  • A high inverse correlation existed between the dose rate of S-23 and the percentage of fat mass in rats.
  • S-23 lowered leptin levels significantly in castrated subjects.

Leptin is a hormone predominantly made by adipose cells and enterocytes in the small intestine that helps regulate energy balance by inhibiting hunger, which diminishes fat storage in adipocytes. Leptin acts on cell receptors in the arcuate nucleus of the hypothalamus.

In simple terms, this can help to lower body fat accumulation.

  • The highest dose (0.75 mg/d) they found, S-23, demonstrated quantitative maintenance of spermatogenesis with an average subnormal testicular of that observed in vehicle-treated animals. (This finding is consistent with several studies using Testosterone to restore spermatogenesis in rats.)
  • The highest dose showed a very high level of suppression on LH (luteinizing hormone) levels and significantly suppressed FSH (follicle-stimulating hormone) concentrations. FSH plays a crucial role in spermatogenesis by maintaining the amount of sperm produced in adult male subjects. (But the suppression went away after discontinuing S-23)

IS S-23 legal in the USA?

Yes. You may possess, and research SARMs, but they have not been approved by the FDA for human usage. This means you should not use them as a supplement; they cannot be used in sports as a way of performance enhancement (that is illegal as they are completely banned in sports.) They also should not be used as a medication to treat illness as there is not enough research to justify such usage.

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