S-23

ID: s23

Aliases: Mastorin, S23

Type: compound

Route/form: oral preclinical SARM context

Status: research

Evidence level: preclinical

Best data tier: non-human experimental

Support scope: non-human/mechanistic, review/regulatory

Source types: preclinical, review

Linked sources: 2

Broad outcomes: Fat loss / metabolic health, Hormones / fertility / sexual health, Muscle growth / performance / recovery, PEDs / AAS / thermogenics, Safety / regulatory

Reading note: These are curation notes anchored to linked sources, not a clinical recommendation or protocol.

Targets / mechanism

• androgen receptor modulator
• nonsteroidal SARM

Optimization domains

• SARM
• male contraception
• fertility
• body composition
• doping

Research basis

• Preclinical male-contraception work shows potent AR modulation with reversible suppression endpoints in rats when paired with estrogen.
• It is a useful counterexample that SARM pharmacology can be intentionally anti-fertility rather than fertility-preserving.
• Any physique rationale is extrapolated from tissue-selective AR biology rather than direct human performance evidence.

Limits, risks, and missing evidence

• No human performance or recovery evidence was identified.
• Fertility suppression is a feature in the main preclinical rationale, making casual PCT or half-natural framing incoherent.
• Product identity, endocrine suppression, lipid/liver monitoring, and doping risk remain unresolved.

Risk flags

• research compound
• preclinical only
• male contraception signal
• fertility suppression
• doping

Linked papers, labels, and reviews

1. Preclinical characterization of S-23 for hormonal male contraception
   preclinical / pubmed_s23_male_contraception_2009
   Rat male-contraception model using S-23 with estradiol benzoate.
2. Selective androgen receptor modulators in preclinical and clinical development
   review / pubmed_sarms_preclinical_clinical_2009
   SARM class review covering multiple preclinical and early clinical programs.