Follistatin
Also Known As: FST, Follistatin 344, FS-344, Follistatin-344, FST344, Activin-binding protein, Myostatin inhibitor protein, Follistatin 288, FS-288, Follistatin peptide, Anti-myostatin, Muscle growth factor, Follistatin recombinant, FST-344 peptide, FST-344, myostatin inhibitor
Follistatin is a research-grade Endogenous glycoprotein / activin-binding protein targeting Myostatin studied in Muscle Growth & Performance research. It is supplied strictly for in vitro laboratory research use only - not for human or animal consumption, and not FDA-approved.
Evidence Tier: Preclinical - Evidence is animal or in-vitro; no human efficacy data.
A myostatin-blocking protein studied for muscle growth, mostly via gene therapy; banned in sport.
At A Glance
| Category | Muscle Growth & Performance |
|---|---|
| Compound Class | Endogenous glycoprotein / activin-binding protein (recombinant) |
| Molecular Target | Myostatin (GDF-8) and activin A neutralization; prevents TGF-beta superfamily inhibition of muscle growth |
| Molecular Weight | 38000 Da |
| Amino Acid Sequence | 344-residue glycoprotein |
| CAS Number | not standardized |
| Half-Life | ~2 hours |
| WADA Status | prohibited |
| Evidence Tier | Preclinical |
Mechanism Of Action
It permanently binds to and traps a protein called myostatin. Since myostatin is the exact chemical signal that tells muscles to stop growing, trapping it allows muscles to grow unrestricted.
Studied For
- Muscle hypertrophy
- Myostatin inhibition
- Female fertility
- Lean muscle mass increase
- Anti-myostatin therapy
- Duchenne muscular dystrophy models
- Muscle wasting / sarcopenia research
- Strength gain research
- Body recomposition
- Ovarian follicle development
- Reproductive hormone regulation
- FSH inhibition
- Activin neutralization
- Anabolic signaling amplification
- Muscle fiber growth
- Fat mass reduction via muscle increase
- Athletic performance research
- muscle growth
- hypertrophy
- bodybuilding
- muscle wasting
- sarcopenia
Reported Research Findings
Animal gene-therapy studies show large, durable muscle gains. Human data are minimal and limited to localized gene therapy. Injected recombinant peptide is rapidly cleared, a key limitation.
Safety And Handling Notes
Sparse human data; theoretical reproductive, cardiac, and tumor-microenvironment effects from broad systemic myostatin and activin blockade.
No approved human use; recombinant peptide pharmacokinetics are poor. WADA-prohibited (myostatin inhibitor). Research use only.
Regulatory Status
Not FDA-approved; experimental. Named on the WADA 2026 Prohibited List under S4.3 as a myostatin-binding protein; prohibited at all times and a non-Specified substance.
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