- Chemical name / synonyms: S‑23. Wikipedia+1
- CAS number: 1010396‑29‑8 Wikipedia
- Mechanism of action: S-23 is a non‑steroidal selective androgen receptor modulator (SARM). It binds to the androgen receptor (AR) with high affinity (K_i ≈ 1.7 nM) and exhibits tissue selectivity — anabolic effects in muscle and bone, with a more favorable anabolic:androgenic ratio than some older compounds. Wikipedia+2PMC+2
- Intended / investigated uses: Originally developed as a potential male hormonal contraceptive — animal studies demonstrated dose‑dependent suppression of spermatogenesis with reversible effects after cessation. Wikipedia+2PMC+2
- Experimental status: As of now, S-23 remains investigational. It is not approved by regulatory agencies for any medical or therapeutic use. Wikipedia+1
Preclinical Findings: Pharmacology, Effects, and Biological Activity
- In animal studies (rats/mice), S-23 produced anabolic effects on skeletal muscle — increasing muscle mass (e.g., levator ani muscle weight) with relatively lower androgenic effects on reproductive tissues, compared to traditional androgens. PMC+2ResearchGate+2
- In those same studies, S-23 suppressed spermatogenesis in a dose-dependent manner; critically — this suppression was reversible upon discontinuation, making S-23 a candidate for male hormonal contraception. PMC+1
- Additional preclinical data suggest S‑23 could have favorable effects on bone mineral density and bone mass, and possibly fat mass reduction — aligning with typical SARM-target tissue selectivity (muscle, bone, metabolic tissues) rather than broad androgenic effects. Translational Andrology and Urology+2PMC+2
- Pharmacokinetics & metabolism: Recent analytical studies (e.g. in vitro metabolite characterization) have documented metabolites of S‑23, which is relevant for detection in doping/analytical contexts. ScienceDirect+1
Potential Benefits (Based on Preclinical Data)
- Muscle mass / lean‑body mass increase — S‑23 showed anabolic effects in muscle in animal models. PMC+2ResearchGate+2
- Bone health / bone mass / bone density — Preclinical evidence suggests possible bone-anabolic or bone‑preserving effects. Translational Andrology and Urology+2PMC+2
- Fat mass reduction / metabolic effects — Some studies noted decreased fat mass in animal models using S‑23. Translational Andrology and Urology+1
- Male contraceptive potential — Due to its capacity to suppress spermatogenesis reversibly while maintaining anabolic effects, S-23 has been studied as a candidate for hormonal male contraception. PMC+1
- Tissue-selective androgen receptor modulation — As a SARM, S‑23 was designed to provide anabolic benefit (muscle, bone) while minimizing androgenic side effects (e.g., prostate enlargement) compared to classical androgens. PMC+2Wikipedia+2
Known Risks, Concerns, and Limitations
- Lack of human clinical data: To date, the publicly available evidence on S‑23 is from animal/preclinical studies. There are no robust published human clinical trials demonstrating safety or efficacy in humans. Wikipedia+1
- Regulatory status — unapproved: S-23, like all SARMs, is not approved by major regulatory authorities (e.g., the U.S. FDA) for any medical use. Marketing, sale, or consumption as a supplement or drug is not legally sanctioned. Wikipedia+2OPSS+2
- Potential for serious adverse effects (by analogy with other SARMs / reported cases): Use of SARMs has been associated with adverse events including liver injury, altered lipid profiles, hormonal disruption, and possible cardiovascular risks. PMC+2Cleveland Clinic+2
- Uncontrolled quality, purity, dosing, and formulation (if acquired outside regulated research): Many SARMs sold online are unregulated — risk of contamination, mislabeling, incorrect dose, impure compound — which increases the likelihood of unpredictable adverse outcomes. Wikipedia+2ScienceDirect+2
- Safety concerns from broader SARM class: Although S-23 has not itself been studied long-term in humans, SARMs as a class have drawn warnings from health authorities about risks such as liver toxicity, heart problems (heart attack, stroke), psychiatric effects, infertility, and organ damage. Cleveland Clinic+2U.S. Food and Drug Administration+2
- Ethical / legal / doping issues: S‑23 is banned by sports‑regulatory bodies (e.g., World Anti-Doping Agency, WADA) — use by athletes constitutes doping. WebMD+2PubMed+2
Interpretation: Where S‑23 Stands Scientifically (As of Now)
S‑23 remains a research compound. While preclinical data in animals are intriguing — showing anabolic effects on muscle and bone, fat reduction, and reversible suppression of spermatogenesis — there is no publicly available evidence about safety or efficacy in humans. The compound has not undergone clinical trials (or at least none have been published). Given the known risks associated with SARMs generally — including possible liver injury, cardiovascular issues, hormonal disruption — any use outside strictly controlled research would carry substantial and unpredictable risk.
Thus, from a scientific and medical standpoint, S‑23 cannot be considered “safe” or “effective” for muscle building, bodybuilding, performance enhancement, contraception, or any therapeutic use — except within rigorously regulated research settings.
For these reasons, any interest in S‑23 must be approached with caution, and only under proper clinical or laboratory protocols, not taken as a supplement or performance enhancer.
Frequently Asked Questions (FAQ) about S‑23
- What is S‑23 and what is its CAS number?
- S‑23 is a selective androgen receptor modulator (SARM), designed to bind androgen receptors selectively to stimulate anabolic effects in muscle and bone. Its CAS number is 1010396‑29‑8. Wikipedia
- Is S‑23 approved for medical use in humans?
- No. S‑23 is investigational only. It has not been approved by regulatory agencies (e.g., FDA) for any medical or therapeutic indication. Wikipedia+1
- What benefits have been observed with S‑23 (in studies)?
- In preclinical (animal) studies, S‑23 increased skeletal muscle mass, improved bone mineral density, reduced fat mass, and suppressed spermatogenesis (with reversibility) — suggesting potential for muscle/bone health and male contraception. PMC+2Translational Andrology and Urology+2
- Has S‑23 been tested in humans (for safety or effectiveness)?
- No publicly available clinical trials in humans have been published. Thus, safety, efficacy, pharmacokinetics, long-term effects remain unknown.
- What are the potential risks or side effects associated with S‑23 (or SARMs generally)?
- While S‑23-specific data in humans don’t exist, SARMs in general have been associated with risks including liver injury, altered lipid profiles, hormonal disruption, cardiovascular risks, and possibly psychiatric or reproductive side effects. PMC+2Cleveland Clinic+2
- Could S‑23 be used as a male contraceptive?
- In animal studies, S‑23 suppressed spermatogenesis in a dose‑dependent manner, with restoration after stopping the drug — suggesting potential as a reversible male contraceptive. PMC+1
- However — because it has not been tested in humans — this remains speculative; no human data confirm contraceptive safety, effectiveness, or reversibility.
- Are SARMs such as S‑23 legal / allowed for athletes?
- No — SARMs are unapproved drugs. They are banned under doping rules (e.g., by WADA), and marketing them as dietary supplements or performance enhancers is generally illegal. NPC Hello+2OPSS+2
- What are the problems with “buying S‑23 online / black‑market use”?
- S‑23 from unregulated sources may be impure, mislabeled, contaminated, or dosed incorrectly — raising major risks. The purity, formulation, sterility, and actual compound identity can all be questionable. ScienceDirect+2Wikipedia+2
- Why are SARMs, including S‑23, considered “dangerous” by medical experts?
- Because they alter hormone signaling, affect lipid and liver function, may increase risk of serious organ damage, and lack long-term human safety data. Regulatory and medical authorities warn against their use outside research. Cleveland Clinic+2PMC+2
- Given what is known — is S‑23 “worth investigating”?
- From a scientific/research standpoint: yes — S‑23 remains of interest, especially for potential anabolic therapy (muscle, bone) or male contraception. But to move forward safely requires rigorous controlled studies in humans to define effective dose, safety profile, long-term effects, and risk/benefit balance.
- From a recreational or “body‑building” standpoint: no — given lack of human data, unknown risks, unregulated quality, and legal/ethical/regulatory issues, the risks appear to strongly outweigh any speculative benefit.
Key Limitations in Current Knowledge
- Almost all data on S‑23 come from animal studies. There is a complete lack of peer-reviewed human clinical trials.
- Long‑term safety (chronic dosing) is totally uncharacterized. Potential long-term toxicity, organ damage, metabolic disturbances, fertility effects in humans remain unknown.
- Real-world use (if acquired outside regulated research) risks high variability in purity, dosage, and possible contamination — making any outcomes unpredictable.
- Regulatory/legal status is prohibitive; S‑23 remains a research chemical, not an approved drug.
- Observed dangers in other SARMs raise the possibility that S‑23 may have similar or even worse adverse effects.
Conclusion (As of Current Evidence)
S‑23 is a potent, tissue-selective SARM that — in preclinical models — demonstrates anabolic effects on muscle and bone, fat reduction, and reversible suppression of spermatogenesis, making it a candidate of interest for therapeutic applications such as muscle wasting, osteoporosis, or male contraception. However, due to the lack of human data, unapproved status, safety concerns associated with SARMs generally, and regulatory/ethical issues, S‑23 cannot — at present — be considered a safe, effective, or approved compound for human therapeutic or recreational use.
Any consideration of S‑23 use outside the context of regulated scientific research carries substantial risk and uncertainty.
