Follistatin / FST-344
Endogenous myostatin + activin binding protein. Inhibits myostatin → drives skeletal-muscle hypertrophy + body-comp shift. Grey-market peptide (FST-344) is the synthetic analog of the 344-aa serum isoform.
How it clearsHalf cleared in ~2d. Most (~96%) gone by ~8d.
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This compound sits in research-grey territory. The caveats below carry more weight than for FDA-approved entries — read them.
Acrush in interest after Bryan Johnson's Oct 2023 follistatin gene-therapy experiment (BioViva-style AAV vector). Grey-market injectable peptide form (FST-344) emerged in 2024-25 to satisfy the spillover demand. Mouse + non-human-primate data documents 15-40% muscle-mass gain over 8-12 weeks. Zero published human RCT of injectable FST-344. The gene-therapy version (single-dose AAV) is a completely different risk profile from the daily/weekly peptide protocol biohackers run.
Zero published human RCT of injectable FST-344. Mouse + primate data drove the hype + Bryan Johnson's experiment publicized it. Long-term myostatin suppression has un-modeled cardiac + tendon-rigidity concerns. Identity verification of grey-market product is poor. Don't conflate the gene-therapy version (single-dose AAV) with the daily/weekly peptide.
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- DMechanistic / anecdotal
Follistatin / FST-344 — primary mechanism: endogenous myostatin + activin binding protein. inhibits myostatin → drives skeletal-muscle hypertrophy + body-comp shift. grey-market peptide (fst-344) is the synthetic analog of the 344-aa serum isoform.
2 supporting referencesVerified 13d ago
External links to PubMed searches, ClinicalTrials.gov, and FDA materials. We do not host papers — we point at canonical sources.
Research-grey · no FDA pathway · gene-therapy version is investigational
Pre-filled with this compound's published dose range: 100-500 mcg · 2-3× weekly, subcutaneous
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