S23 Research Overview (also known as S-23, S23 SARM, Selective androgen receptor modulator S23)
S23 is an experimental, nonsteroidal selective androgen receptor modulator (SARM) developed for research into androgen-receptor biology, muscle-related endpoints, and male reproductive suppression. It has demonstrated tissue-selective androgenic activity in preclinical models, but it is not an approved human therapeutic and lacks established clinical dosing, efficacy, or safety data.
What Is S23?
S23 is an investigational selective androgen receptor modulator, or SARM, belonging to a class of synthetic ligands designed to activate the androgen receptor in a tissue-dependent manner. Unlike testosterone and other broadly acting anabolic-androgenic steroids, SARMs were developed with the goal of producing stronger anabolic activity in skeletal muscle and bone while reducing some androgenic effects in tissues such as the prostate and skin. S23 is one of the more potent experimental SARMs described in the preclinical literature and has been studied primarily in rodents rather than in controlled human trials.
Research interest in S23 centers on skeletal-muscle signaling, lean-mass and strength-related outcomes, body-composition models, androgen-receptor selectivity, and reproductive endocrinology. In male animal studies, S23 has also been investigated for its ability to suppress spermatogenesis and circulating reproductive hormones, which has led to interest in its potential as a component of a male hormonal-contraception strategy. These findings should not be interpreted as evidence that S23 is suitable for contraception, athletic performance, or self-directed use. S23 is not an approved medicine, and its long-term effects in humans remain undefined.
Research Indications
Androgen Receptor Pharmacology
Selective androgen receptor modulation
S23 is a nonsteroidal selective androgen receptor modulator studied for high-affinity androgen receptor binding and tissue-selective androgenic and anabolic signaling in experimental systems.
Oral bioactivity in animal models
Published preclinical work describes oral activity in rodents, with effects assessed using androgen-responsive tissue, body-composition, and reproductive endpoints.
Lean Mass and Physical Function Research
Muscle preservation models
Animal research has evaluated S23 for anabolic activity and maintenance of androgen-responsive tissue; these findings cannot establish efficacy for muscle gain or performance in humans.
Bone-related endpoints
SARMs have been investigated broadly in preclinical bone-loss models, but there is no established clinical role or approved therapeutic indication for S23.
Male Contraception Research
Suppression of the hypothalamic-pituitary-gonadal axis
Rodent studies report marked suppression of gonadotropin-dependent reproductive function, a pharmacologic effect that is a major safety concern rather than a validated human contraceptive approach.
Fertility endpoints
Preclinical contraception findings do not demonstrate reliable, reversible, or safe contraception in people. S23 is not approved for contraceptive use.
Human Evidence Status
No approved medical indication
S23 is not an approved medicine. Robust human efficacy, pharmacokinetic, and long-term safety data are not available for recreational or performance-oriented use.
Regulatory and sport status
SARMs are prohibited in sport under the World Anti-Doping Agency Prohibited List, and products marketed as research chemicals may have substantial identity and purity uncertainty.
Research Protocols
As reported in cited literature and research-community logs (see Research Citations below) — not a personal dosing recommendation.
| Research Application | Dose | Frequency | Route |
|---|
| Published rodent pharmacology | 0.1–0.75 mg/kg | Daily in animal studies | Oral |
| Male contraception animal models | 0.1 mg/kg | Daily in animal studies | Oral |
| Human research reference | No established dose | Not established | Oral |
| Nonclinical analytical research | Method-dependent | Protocol-dependent | Oral |
Timing
Human timing, half-life, accumulation, and recovery intervals have not been adequately established. Animal dosing schedules cannot be converted directly into a safe or effective human protocol. S23-associated endocrine suppression may persist beyond exposure and warrants clinician-directed evaluation rather than self-managed timing.
Peptide Interactions
Combined androgenic exposure may compound lipid, blood-pressure, hepatic, psychiatric, and endocrine risks. There is no established safety basis for stacking.
Alcohol can add hepatic and cardiometabolic burden and may obscure adverse effects. Avoiding concurrent use is prudent when liver safety is uncertain.
Agents with potential liver toxicity, including high-dose acetaminophen and certain prescription medicines, may increase concern when product composition and S23 hepatic risk are uncertain.
SARM-class exposure may adversely affect lipoprotein markers. Changes in lipids should be interpreted by a clinician, particularly in people receiving cardiovascular risk treatment.
S23 has been investigated specifically for suppression of male reproductive function in animals and should not be used during attempts to conceive or alongside fertility-directed care.
No specific pharmacokinetic interaction is established; however, stimulant-related increases in heart rate, anxiety, or blood pressure can complicate monitoring of adverse symptoms.
Reported Research Timeline
01First days (reported in cited studies): no validated human onset profile exists. Early subjective changes reported outside research are not reliable measures of pharmacologic effect or product identity.
02Weeks 1–2 (reported in cited studies): endocrine signaling may already be affected; changes in libido, mood, sleep, acne, or energy can occur with androgenic agents but are nonspecific.
03Weeks 2–4 (reported in cited studies): laboratory changes, including testosterone-axis suppression and adverse lipid changes, may be more informative than subjective effects and require clinical interpretation.
04Weeks 4–8 (reported in cited studies): continued exposure may increase cumulative endocrine and cardiometabolic concern. There is no established safe duration for human use.
05After discontinuation (reported in cited studies): recovery of hypothalamic-pituitary-gonadal function is variable and cannot be predicted from animal studies or online reports.
06Weeks to months after discontinuation (reported in cited studies): persistent low libido, fatigue, depressed mood, infertility concerns, or abnormal laboratory results warrant medical assessment rather than self-treatment.
Safety Notes
Included for harm-reduction awareness only, in the event this compound is encountered outside its labeled research use. Inclusion here does not imply RUO Codes endorses, recommends, or instructs human use.
S23 is an investigational SARM and is not approved for medical, performance, or contraceptive use in humans.
Marked suppression of endogenous testosterone and reproductive function has been observed in animal research; fertility and recovery effects in humans are uncertain.
Avoid use during pregnancy, breastfeeding, adolescence, active attempts to conceive, or in the presence of androgen-sensitive disease unless specifically directed by a qualified clinician.
Potential class concerns include reduced HDL cholesterol, altered liver enzymes, blood-pressure changes, acne, hair changes, mood effects, and sexual dysfunction.
Products sold as S23 may be mislabeled, underdosed, contaminated, or substituted with other pharmacologically active substances.
Seek Medical Attention If:
You develop chest pain, shortness of breath, fainting, a sustained rapid heartbeat, or new one-sided weakness.
You notice yellowing of the skin or eyes, dark urine, pale stools, severe abdominal pain, or persistent vomiting.
You experience severe depression, agitation, suicidal thoughts, mania, or other major changes in mental state.
You have persistent testicular pain, profound fatigue, sexual dysfunction, or fertility concerns after exposure or discontinuation.
Quality Indicators
Verified Marker
Lot-specific third-party COA
A certificate of analysis should identify the exact lot, test date, laboratory, sample identifier, analytical method, and result rather than providing a generic manufacturer document.
Verified Marker
Identity confirmation by LC-MS or LC-MS/MS
Identity testing should compare the sample against an appropriate reference standard and report the analytical technique, chromatogram or mass-spectral evidence, and acceptance criteria.
Verified Marker
Quantitative HPLC or UPLC assay
For oral products, assay results should report actual S23 content, stated-unit content, analytical uncertainty, and whether degradation products or related substances were evaluated.
Acceptable Range
Tablet or capsule mass accuracy
Uniformity of dosage units and fill-weight variation should be documented. A purity percentage alone does not verify the milligram amount per oral unit.
Quality Concern
Generic COAs, unsupported claims, or missing contaminant testing
Avoid relying on unverifiable PDFs, reused batch numbers, “research use only” labeling as a quality claim, or products without testing for residual solvents, heavy metals, and microbial contamination where applicable.
Research Citations
- S-23, an orally active nonsteroidal selective androgen receptor modulator, is a potent male contraceptive in rats.
Chen, J., Hwang, D. J., Bohl, C. E., et al., 2010, Endocrinology - The safety, pharmacokinetics, and effects of LGD-4033, a novel nonsteroidal oral selective androgen receptor modulator, in healthy young men.
Basaria, S., Jasuja, R., Huang, G., et al., 2013, Journals of Gerontology Series A - The selective androgen receptor modulator GTx-024 (enobosarm) improves lean body mass and physical function in healthy elderly men and postmenopausal women: results of a double-blind, placebo-controlled phase II trial.
Dalton, J. T., Barnette, K. G., Bohl, C. E., et al., 2011, Journal of Cachexia, Sarcopenia and Muscle - Gonadal steroids and body composition, strength, and sexual function in men.
Finkelstein, J. S., Lee, H., Burnett-Bowie, S. A. M., et al., 2013, New England Journal of Medicine - The effects of supraphysiologic doses of testosterone on muscle size and strength in normal men.
Bhasin, S., Storer, T. W., Berman, N., et al., 1996, New England Journal of Medicine
Research Focus
androgen receptor pharmacology, muscle hypertrophy, strength, body composition, anabolic signaling, spermatogenesis suppression, male hormonal contraception, endocrine safety
Frequently Asked Questions
What should researchers watch for with S23?
Included for harm-reduction awareness only, in the event this compound is encountered outside its labeled research use. Inclusion here does not imply RUO Codes endorses, recommends, or instructs human use.
What should researchers expect over time with S23?
First days (reported in cited studies): no validated human onset profile exists. Early subjective changes reported outside research are not reliable measures of pharmacologic effect or product identity.
How is S23 typically administered in research?
As reported in cited literature and research-community logs (see Research Citations below) — not a personal dosing recommendation.
Browse all peptides in the Encyclopedia →