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Follistatin 344 (Myostatin Inhibitor)
Also known as: FST344, Follistatin, FS344, ACE-031 (related)
Confidence
Updated 2026-03-18
Follistatin 344 is a naturally occurring glycoprotein that binds and neutralizes myostatin, activin, and other TGF-beta superfamily members that inhibit muscle growth. The 344-amino acid isoform is the full-length, broadly acting variant. Interest in follistatin surged after gene therapy studies demonstrated dramatic muscle hypertrophy in animals. It is one of the most sought-after compounds in the bodybuilding and muscle-wasting disease communities.
Class
Myostatin Inhibitor / Muscle Growth
Routes
Subcutaneous, Intramuscular
Half-Life
Not established in humans for injectable form. Endogenous follistatin: ~2–3 hours.
Follistatin 344 binds to and neutralizes myostatin (GDF-8), activin A, and other TGF-beta superfamily ligands with high affinity. By sequestering myostatin, it removes the primary endogenous brake on skeletal muscle growth, allowing enhanced myogenesis and muscle hypertrophy. It also modulates FSH release (follistatin was originally discovered for its role in suppressing FSH), influences fat metabolism, and may protect against fibrosis. The 344 isoform circulates systemically and affects multiple tissues.
Half-Life
Not established in humans for injectable form. Endogenous follistatin: ~2–3 hours.
Bioavailability
Not established for injectable recombinant follistatin. Gene therapy approaches bypass bioavailability concerns.
No approved indications. Research: muscle wasting (sarcopenia, cachexia), muscular dystrophy, body composition optimization, fertility (activin/FSH modulation).
Animal studies: Dramatic — follistatin gene therapy in mice and non-human primates produced significant muscle hypertrophy and strength gains. AAV1-follistatin gene therapy Phase I/II trial at Nationwide Children's Hospital for Becker MD (n=6) showed improved 6-min walk distance with favorable safety. For injectable recombinant follistatin: essentially no human clinical trial data. The evidence supporting injectable follistatin use is based on extrapolation from gene therapy, related myostatin inhibitor drug trials, and in vitro/animal studies.
Human Studies
3
Animal Studies
50
Gene therapy studies: generally well-tolerated in small trials. Injectable recombinant: unknown safety profile. Theoretical concerns: FSH suppression (potential fertility impact, especially in women), uncontrolled muscle growth, tendon/ligament stress from rapid strength gains, effects on cardiac muscle (myostatin inhibition affects heart), potential tumor promotion (TGF-beta superfamily involvement in cancer suppression).
Investigational. No injectable form in clinical development. Gene therapy approaches in early-phase trials for muscular dystrophy. Available as a research peptide — but recombinant protein quality and bioactivity vary enormously among suppliers.
Drug Interactions: May interact with TGF-beta pathway drugs, fertility medications (FSH modulation). Monitoring: FSH, LH, testosterone/estradiol, muscle mass assessments, cardiac function. Research Gaps: No human data for injectable recombinant follistatin. Purity and bioactivity of commercial research preparations not verified. Dose-response, PK, and safety completely unknown for injection use.
Subcutaneous (research context — no validated protocol)
Common Range
100–300 mcg/day (anecdotal research community protocols — NOT clinically validated)
Timing
Variable
Frequency
Daily for 10–30 days (anecdotal)
Cycling
10–30 day cycles (anecdotal)
Reconstitution
Reconstitute lyophilized recombinant protein with bacteriostatic water. Handle gently — proteins can denature.
Storage
Refrigerated. Highly sensitive to temperature and agitation.
Important Note
NOT FDA-approved. NO validated human dosing data for injectable use. Protein quality from research suppliers is highly variable. Extreme caution warranted. Research context only.
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Tissue Repair & Regeneration
BPC-157 is a synthetic pentadecapeptide derived from a protective protein found in human gastric juice. It has generated extraordinary interest for its broad cytoprotective and regenerative effects observed in preclinical studies across virtually every organ system studied. Despite this promise, it remains one of the most controversial peptides due to the near-complete absence of human clinical trial data.
Tissue Repair & Regeneration
TB-500 is a synthetic version of thymosin beta-4, a naturally occurring 43-amino acid protein fragment that plays critical roles in tissue repair, cell migration, and anti-inflammatory processes. Combined with BPC-157, it forms what is colloquially known as "the Wolverine stack" in regenerative wellness circles. Like BPC-157, its clinical evidence base is limited to preclinical data.
Disclaimer: This content is for educational and informational purposes only and does not constitute medical advice. Always consult with a licensed healthcare provider before starting, stopping, or modifying any peptide therapy. PeptideSupplierMatch does not prescribe, sell, or distribute peptides.
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