Follistatin 344
Activin-binding glycoprotein that inhibits myostatin, potentially promoting muscle growth beyond normal genetic limits.
🔬 Mechanism of Action
Follistatin 344 is a monomeric glycoprotein that binds and neutralizes myostatin (GDF-8) and activins with high affinity. Myostatin is the primary negative regulator of muscle growth — it acts as a "brake" that limits skeletal muscle size.
By binding myostatin, Follistatin removes this brake, allowing increased muscle protein synthesis and hypertrophy beyond normal genetic limits. The "344" refers to the specific isoform (344 amino acids) that provides the broadest myostatin/activin neutralization. Animals with natural myostatin gene deletions (Belgian Blue cattle, Mighty Mouse) display extreme musculature.
Source: PMID: 17108139
📜Background & History
Follistatin-344 is an isoform of follistatin — a glycoprotein first purified from ovarian follicular fluid in 1987 by four independent research groups. Follistatin's primary mechanism is sequestration of myostatin (GDF-8), the master inhibitor of muscle growth. By binding and neutralizing myostatin, follistatin removes the physiological brake on muscle hypertrophy. The -344 isoform has high heparan sulfate binding affinity, concentrating it in muscle tissue. A single intramuscular gene therapy injection of follistatin in animal models produced up to 2× muscle mass increase.
🎯 Research Use Cases
- ✓Muscle wasting diseases: muscular dystrophy, sarcopenia
- ✓Muscle hypertrophy research with myostatin inhibition
- ✓Cancer cachexia management
- ✓Athletic performance research (banned in sport)
💉 Dosing Protocol
| Typical Dose | 100-300 mcg/day |
| Frequency | 1× daily for 10-30 days |
| Half-Life | ~3-6 hours (estimated) |
| Common Vial Sizes | 1 mg |
🧪 Reconstitution Example
⚠️Safety & Considerations
Research peptide. Potent effects on muscle growth pathway. Also affects FSH levels (follistatin was originally named for its role in FSH regulation). May impact fertility — monitor reproductive hormones. Very limited human safety data.
⚡Interactions & Contraindications
Ban: WADA anti-doping — prohibited in competitive sport. Long-acting: effects may last weeks to months per injection. Potential interaction with reproductive hormone axis (FSH inhibition) — monitor in women. Improperly sourced follistatin carries bacterial contamination risk; source quality is critical.
🔗Synergies & Common Stacks
Follistatin removes the myostatin brake on muscle growth; IGF-1 LR3 simultaneously drives the anabolic signaling. Additive muscle hypertrophy potential.
GH/IGF-1 elevation (Ipamorelin) provides anabolic substrate while follistatin maximizes the muscle's capacity to respond by inhibiting myostatin.
❓ Frequently Asked Questions
Can Follistatin really inhibit myostatin?▼
Does Follistatin affect fertility?▼
📖 References
- Haidet AM, et al. “Follistatin administration stimulates muscle growth in mice.” J Clin Invest (2008). PMID: 18769635