Follistatin-344, what the science actually shows

Follistatin-344 is a recombinant peptide that binds and inhibits myostatin, studied for muscle growth. Not FDA-approved. Evidence base: primarily animal studies; limited human data.

A naturally occurring glycoprotein that binds and neutralizes myostatin, the body's 'muscle growth brake.' Gene therapy research is active. The bodybuilding community's most discussed protein for theoretical muscle growth beyond natural limits.

Evidence
★★☆☆☆ Limited
Type
Glycoprotein
Structure
344 amino acids

What Follistatin-344 is

Glycoprotein first identified in ovarian follicular fluid (1987). Multiple isoforms: FS-288 (tissue-bound), FS-303, FS-344 (circulating). FS-344 is the full-length circulating form. Its connection to muscle comes from binding and neutralizing myostatin.

Mechanism, in plain English

Myostatin signals muscle cells to stop growing. Animals with myostatin deletions (Belgian Blue cattle, 'mighty mice') have dramatically increased muscle. Follistatin binds myostatin with high affinity, releasing the brake on muscle growth. Also binds activin A and GDF-11. Broad binding profile affects multiple systems.

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What the evidence shows

Gene therapy in mice/primates produces significant muscle hypertrophy without exercise. Human gene therapy trials (Nationwide Children's Hospital) for muscular dystrophy show safety and preliminary efficacy. Exogenous protein injection has poor pharmacokinetics, rapid clearance. Gene therapy approach is more promising but years from availability.

FDA status

Not FDA-approved. Gene therapy trials ongoing for muscular dystrophy. WADA monitors myostatin inhibitors.

Common synonyms

Follistatin-344, FS-344, FST-344, activin-binding protein

Safety and adverse-event landscape

Gene therapy trials: acceptable safety. Exogenous protein: extremely limited data. Theoretical concerns: reproductive effects (activin inhibition), cancer biology (TGF-beta pathway).

Frequently asked questions

In animal gene therapy, yes. Injectable protein in humans: unproven (pharmacokinetic challenges).
Technically a glycoprotein (344 amino acids). Included due to prominence in the peptide/bodybuilding community.
Not a controlled substance. WADA monitors myostatin inhibitors. Gene doping is prohibited.
No. Peptexa is educational only.

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