Follistatin 344
Aliases: FST344 · FS344
Last verified: 2026-09-23
The short version
A regulatory glycoprotein that binds and neutralizes myostatin and activin — removing the "brake" on muscle growth. Virally delivered follistatin gene therapy produced dramatic hypertrophy in monkeys. Key fact: Human data are limited: small trials or case-series reports exist, without large randomized studies. Follistatin gene therapy (primate studies; clinical development for muscular dystrophies in related programs). Status: research chemical. Not approved; WADA-banned.
Identity & type
- Molecular type
- peptide
- Origin
- A regulatory glycoprotein that binds and neutralizes myostatin and activin — removing the "brake" on muscle growth.
Mechanism of action
Antagonizes myostatin (GDF-8) and activins via direct binding → disinhibition of muscle growth and gonadal hormones.
not confirmed in humans
Dosing & routes
Official / clinical context
No approved official document exists for Follistatin 344. Any protocols mentioned are to be read as information, not as a recommendation.
Regulator-approved labeling and published study designs — never a recommendation.
Community-reported practice
Experimental: 100 mcg/day SC, 10–30 day cycles. The community reports rapid muscle growth in short cycles, but with side effects: joint pain and "excessive" muscle-mass gain with poor dosing control. All anecdotal; caution is advised.
Unverified self-reports. Not medical advice. Not endorsement.
Expected effects (community)
The community reports rapid muscle growth in short cycles, but with side effects: joint pain and "excessive" muscle-mass gain with poor dosing control. All anecdotal; caution is advised.
Protocol — official vs community
Official / label
No approved protocol exists — investigational agent. Follistatin gene therapy reached primate studies and related programs reached clinical development for muscular dystrophies, but the recombinant peptide itself is preclinical.
Duration: —
The gene-therapy literature is the closest thing to human-adjacent data; the injectable peptide inherits that credibility only by analogy.
Community (anecdotal)
~100 mcg SC daily in animal-model extrapolations circulating in bodybuilding communities; some protocols load higher in week 1. Approximate and unvalidated.
- Cycle:
- 10–30 days, short by design.
- Break:
- Several weeks to months off; no consensus.
The concern that matters is activin inhibition: follistatin does not selectively block myostatin, and suppressing activin signaling has gonadal and reproductive consequences the community literature largely ignores.
Human evidence
Human data are limited: small trials or case-series reports exist, without large randomized studies. Follistatin gene therapy (primate studies; clinical development for muscular dystrophies in related programs).
Preclinical evidence
Follistatin gene therapy (primate studies; clinical development for muscular dystrophies in related programs). Recombinant peptide preclinical only.
Known risks
- Possible joint/tendon issues, hormonal disturbances (activin inhibition), unknown long-term risks.characterized
- Unregulated injectable supply — sterility, purity and accurate dose not assuredtheoretical
Teal: characterized in clinical/labeling contexts. Amber: theoretical or reported outside controlled settings.
Unknowns & evidence gaps
- Long-term human safety
- Optimal dose and pharmacokinetics
Frequently asked questions
References
Systematic references are being expanded; verify sources directly before any decision.