Library · Muscle, bone & joint · Muscle growth enhancement and muscle wasting treatment
Follistatin (FS-315, FS-344)
FS-315, FS-344, Activin-binding protein, FST, Follistatin-related protein
Naturally occurring protein first identified in 1987 as an inhibitor of follicle-stimulating hormone; FS-315 and FS-344 are studied variants for muscle growth and repair. Works by blocking myostatin and related TGF-β family signals; still in the research phase, with synthetic versions unapproved for medical use.
Research score 60/100. Reference only, not a dose.
- Muscle Growth
- Recovery Enhancement
- Anti-aging
- Joint Support
- Hormone Regulation
- US status
- Research Chemical
- Approval
- Research Chemical Only
- Evidence
- Myostatin inhibitor promoting muscle hypertrophy. Investigational gene therapy for Becker Muscular Dystrophy. Peptide use is largely in the 'biohacking' community.
- Research score
- 60 / 100
- Indication
- Muscle Wasting
- Origin
- Japan
- Source category
- Muscles & Joints
- Status group
- Research chemical
Mechanism
Neutralizes myostatin and activin, removing their brake on muscle growth and triggering satellite-cell activation and myoblast proliferation via IGF-1/PI3K/Akt and mTOR signaling; also affects bone metabolism through BMP signaling and lowers inflammatory cytokines.
Safety file
Peptide safety data is mostly anecdotal (muscle soreness, tendon weakness); gene-therapy trials show good safety, but there’s theoretical concern over hormone disruption and mixed cancer-growth effects.
- Injection site reactions
- Potential hormone level fluctuations
- Muscle sensitivity
- Temporary fatigue