Mesterolone (Proviron)
Muscle & Strength · Oral DHT-derivative androgen / TRT adjunct
Tier D+
Bottom line
Read Off Label grades Mesterolone (Proviron) as D+ (3.9/10) based on weak evidence, low-med benefit magnitude, and a med-risk safety profile.
Schering (now Bayer) Proviron — developed 1960s; introduced for medical use 1967.
Studied, labeled, or reported-use context: Therapeutic 25-75 mg/day PO divided; TRT-adjunct biohacker use typically 25-50 mg/day; historical… — NOT FDA-approved in US (never marketed); Schedule III controlled substance under the Anabolic Steroid Control Act; Rx in EU/UK/Asia/Australia/Latin America (Schering/Bayer Proviron); WADA Prohibited List S1; not individualized guidance.
Citation correction in progress
1 PubMed link was found to be unrelated to this entry and removed from public output. The remaining sources are shown below, but this row's claims and score still need a full source-by-source revalidation.
What the evidence says
Schering (now Bayer) Proviron — developed 1960s; introduced for medical use 1967. The distinguishing pharmacology is the 1α-methyl substitution that confers oral bioavailability WITHOUT the C17α-alkylation that gives most oral AAS their characteristic hepatotoxicity — making mesterolone the mildest oral DHT-derivative on hepatic stress (compare with Winstrol/Anadrol/Dianabol). Already 5α-reduced so not a 5α-reductase substrate; NOT aromatizable. **Primary biohacker use case** is as a TRT adjunct: SHBG-binding displaces testosterone from SHBG, raising the free-T fraction; the libido/erectile-quality signal in clinic practice is real but only loosely supported by RCTs. **Monotherapy efficacy is weak**: Nieschlag 1989 (Hum Reprod) — the largest infertility RCT (n=248 couples; 6 months) showed sperm parameter improvement but NO pregnancy benefit. Comhaire 1991 (Fertil Steril) high-dose mesterolone confirmed limited efficacy. **Safety profile vs other orals**: lower hepatotoxicity than C17α-alkylated orals; comparable or worse HDL suppression to other DHT derivatives; strong androgenic effects accelerate androgenetic alopecia and worsen BPH in predisposed men. **Modern trend**: increasingly displaced by aromatase inhibitors (anastrozole) for estrogen control on TRT — Proviron's SHBG-lowering use case remains niche. **NOT FDA-approved in US** — only available via international sources or research-chemical channels; legal risk applies. Distinct from Masteron (drostanolone) — Masteron is injectable, used pre-contest; Mesterolone is oral, used as a TRT adjunct.
Mechanism
1α-methyl-DHT derivative; orally bioavailable via 1α-methyl substitution rather than the more hepatotoxic 17α-alkylation typical of oral AAS; androgen receptor agonist with strong androgenic and weak anabolic profile (inactivated by 3α-HSD in skeletal muscle limits muscle-building effect); NOT a 5α-reductase substrate (already 5α-reduced); NOT aromatizable to estrogen; high SHBG-binding affinity displaces testosterone → increases free testosterone fraction; mild anti-estrogenic activity via 3β-HSD interference
Studied, labeled, or reported dose & route
Therapeutic 25-75 mg/day PO divided; TRT-adjunct biohacker use typically 25-50 mg/day; historical infertility protocols 100 mg/day; food coadministration appears in reported protocols
This records doses and routes described in studies, approved labeling, clinical practice, or documented use. It is not individualized guidance and does not establish safety; context changes with indication, formulation, health history, monitoring, and other medicines.
Citations
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Common questions
- What does the evidence show about Mesterolone (Proviron)'s effects?
- Read Off Label rates the evidence for Mesterolone (Proviron) as Weak and the benefit magnitude as low-med, producing an overall grade of D+ (3.9/10). Schering (now Bayer) Proviron — developed 1960s; introduced for medical use 1967.
- What safety findings are reported for Mesterolone (Proviron)?
- Mesterolone (Proviron) has a med risk profile in the database. Med (strong androgenic effects — accelerated androgenetic alopecia, acne, BPH risk; HDL crash typical of DHT derivatives; HPG suppression; LOWER hepatotoxicity than C17α-alkylated orals because of the 1α-methyl substitution; prostate concerns in older men) Legal status: NOT FDA-approved in US (never marketed); Schedule III controlled substance under the Anabolic Steroid Control Act; Rx in EU/UK/Asia/Australia/Latin America (Schering/Bayer Proviron); WADA Prohibited List S1 (anabolic agents).
- What doses or routes are reported for Mesterolone (Proviron)?
- Therapeutic 25-75 mg/day PO divided; TRT-adjunct biohacker use typically 25-50 mg/day; historical infertility protocols 100 mg/day; food coadministration appears in reported protocols This is context from studies, approved labeling, clinical practice, or documented use; it is not individualized guidance and does not establish safety.
- How does Mesterolone (Proviron) work?
- 1α-methyl-DHT derivative; orally bioavailable via 1α-methyl substitution rather than the more hepatotoxic 17α-alkylation typical of oral AAS; androgen receptor agonist with strong androgenic and weak anabolic profile (inactivated by 3α-HSD in skeletal muscle limits muscle-building effect); NOT a 5α-reductase substrate (already 5α-reduced); NOT aromatizable to estrogen; high SHBG-binding affinity displaces testosterone → increases free testosterone fraction; mild anti-estrogenic activity via 3β-HSD interference
This is an independent synthesis of published research by a non-clinician. Scores are opinions supported by citations, not prescriptions. See the full disclaimer and methodology for how this score was produced and what it does and doesn't mean.