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.
Quick Reference
Member reference tables summarize the compound's research parameters.
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
Preliminary Data
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
Emerging Evidence
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
Preliminary Data
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.
This member section describes parameters reported in the research literature.
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.
This member section discusses research safety considerations and uncertainties.
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.