Follistatin
Endogenous myostatin inhibitor — dramatic muscle growth in animal models; human gene therapy trials underway.
Research facts
| Half-life | Minutes (rapid binding) |
|---|---|
| Route | IM / SubQ (research only) |
| Typical dose | Highly experimental — no established research dose |
| Frequency | Unknown — no standardised human protocol |
| Solvent | Bacteriostatic water |
| pH | 5.5–7.0 |
| Stability | Frozen (-80°C) |
Mechanism of action
Follistatin is an endogenous glycoprotein that functions as a pan-inhibitor of TGF-β superfamily members, most notably activin and myostatin. Myostatin is the primary brake on skeletal muscle growth — "myostatin knockout" animals develop extraordinary muscle mass. Follistatin binds myostatin (and activin) with high affinity, removing this inhibitory brake. In rodents and non-human primates, follistatin gene delivery produces 2–3× increases in muscle mass. Gene therapy trials (follistatin rAAV) in Becker's muscular dystrophy and other myopathies are underway in humans with early positive results.
Documented effects (research-model)
- Theoretical profound muscle growth via myostatin inhibition
- Gene therapy trials positive in muscular dystrophy
- Potential in muscle wasting diseases (cachexia, sarcopaenia)
- Activin inhibition may affect FSH regulation and bone metabolism
Research protocols
| Protocol | Dose | Frequency | Cycle | Vial |
|---|---|---|---|---|
| Research Only | No established human dose — gene therapy models only | N/A | Gene therapy is a one-time application | N/A — not available as injectable research compound |
Research context only. Not medical advice. Consult a qualified healthcare professional before any protocol decision.
Synergies
No documented synergies in the current reference set.
Myths & misconceptions
Evidence gaps
- No human RCT data for injectable follistatin.
- Rapid protein degradation limits injectable bioavailability.
- Follistatin gene therapy is in Phase I/II — long-term safety unknown.
- Systemic activin inhibition could affect reproduction and haematopoiesis.
Safety notes
Injectable follistatin: minimal evidence of benefit but theoretical risks include FSH disruption, reproductive effects (activin regulates FSH), and haematopoietic effects. Gene therapy: experimental, Phase I/II safety data only. Do not inject without understanding the risks.
Biomarkers to monitor
Primary-source citations
- PMID 19834571 — Follistatin gene therapy produces muscle hypertrophy in monkeys (Sci Transl Med. 2009)
Frequently asked
What is Follistatin?
Follistatin (FST — Activin Antagonist and Myostatin Inhibitor) is a research compound classified in our library as Tier C — Limited human trials; effect size uncertain.. Endogenous myostatin inhibitor — dramatic muscle growth in animal models; human gene therapy trials underway.
What is the evidence tier for Follistatin?
We classify Follistatin as Tier C: Limited human trials; effect size uncertain. See our full peptide evidence tiers explainer for how we assign S/A/B/C/D.
What is the research dose of Follistatin?
For Follistatin, typical research dose is Highly experimental — no established research dose, route is IM / SubQ (research only), half-life is Minutes (rapid binding). Protocols vary by research goal — see the protocols section on this page for standard and advanced dosing schedules. Research use only, not medical advice.
Is Follistatin safe?
Injectable follistatin: minimal evidence of benefit but theoretical risks include FSH disruption, reproductive effects (activin regulates FSH), and haematopoietic effects. Gene therapy: experimental, Phase I/II safety data only. Research context only — no compound on this site is approved for human therapeutic use unless explicitly noted.