Also known as FST · FS-288 · FS-315 · follistatin-344
A natural myostatin and activin antagonist — by neutralizing the muscle brake it is one of the most potent pro-muscle factors studied, and a doping and gene-therapy flashpoint.
Follistatin is the body’s own counterweight to myostatin. It is a secreted glycoprotein that binds and neutralizes TGF-β-superfamily ligands — most importantly myostatin and activin — and by mopping up the signals that restrain muscle, it becomes one of the most powerful pro-muscle factors in the research literature. If myostatin is the brake on muscle growth, follistatin takes the foot off it.
Follistatin exists in the body precisely to oppose the activin/myostatin axis, and overexpressing it produces some of the most striking muscle-growth phenotypes in animal research — larger gains than knocking out myostatin alone, because follistatin blocks multiple inhibitory ligands at once. It occurs in several isoforms (the FS-288 and FS-315 forms differ in how tightly they bind to cell surfaces and heparan sulfate), and as a secreted glycoprotein it is a true biologic, not a synthetic peptide.
Most of the serious work on follistatin has been as gene therapy: delivering a follistatin gene (often the FS-344 construct) to muscle has shown durable muscle growth in models and has been explored in early human trials for muscular dystrophies and inclusion-body myositis. That gene-therapy route — rather than injecting the protein — reflects both follistatin’s short half-life and the goal of sustained local expression.
It shares the forward-looking metabolic angle with myostatin: as GLP-1-class drugs drive large weight loss that includes muscle, follistatin-based and myostatin-antagonist approaches are part of the strategy to protect lean mass and improve the *quality* of that weight loss. It is, equally, a doping and hype target — "follistatin" products are marketed far beyond the evidence, and the pathway is banned in sport.
For a reference, follistatin is best framed honestly: a genuinely potent muscle-growth regulator with real promise in muscle-wasting disease and a real frontier role alongside metabolic drugs — but one whose most credible results come from gene therapy in research settings, not from the supplements and injectables sold under its name.
Binds activin and myostatin with high affinity and sequesters them from their receptors, blocking the ActRIIB/Smad2/3 signaling that suppresses muscle growth. The net effect is disinhibition of muscle-fiber growth, studied as both a protein and a gene-therapy payload.
Behind every vial of Follistatin is the same exacting pipeline every research peptide runs — but the chemistry plays out differently for this molecule. Here is how Follistatin, specifically, is brought into being.
On paper, Follistatin weighs in at roughly 34,000 daltons. Before a single bond is made, the target sequence, salt form, and purity threshold are written down as the contract the finished material must meet.
Follistatin is assembled by solid-phase peptide synthesis — the chain grows one protected residue at a time on resin, and what you fail to build cleanly here you pay to remove later.
The crude mixture — Follistatin plus its deletions and side products — is then separated on preparative HPLC, and where the cut is taken decides the difference between a genuinely pure peptide and a barely-passable one.
A real batch of Follistatin proves itself: identity confirmed by mass spectrometry against its ~34,000 Da, purity read directly off an analytical HPLC trace, water and counterion content measured. That batch-specific certificate of analysis is the only honest way to know what is actually in a vial of Follistatin — and a short, cold, accountable chain of custody is how that purity survives the trip to your bench.
Follistatin is a secreted glycoprotein (isoforms ~31–38 kDa with glycosylation), produced recombinantly in eukaryotic cells rather than by solid-phase synthesis; its mass varies with isoform and glycosylation, so it has no single molecular formula. Much of the credible therapeutic work uses follistatin gene delivery, characterized as a gene-therapy product, with the expressed protein verified by glycoprotein-grade analytics.
Don't judge a vial by its cake. A fluffy, good-looking lyophilized powder reflects bulking agents and freeze-drying parameters — not purity. Insist on a batch-specific certificate of analysis.
Recent clinical trials and publications mentioning Follistatin, pulled automatically from ClinicalTrials.gov and PubMed and refreshed daily. Listings are unfiltered search results, not curated endorsements.
A secreted glycoprotein that binds and neutralizes myostatin and activin, removing the brakes on muscle growth. It is one of the most potent pro-muscle factors in research, studied mainly as a gene therapy.
Myostatin restrains muscle growth; follistatin blocks myostatin (and activin), so it does the opposite. Follistatin can exceed the muscle gains of removing myostatin alone because it neutralizes several inhibitory signals.
The most credible results come from follistatin gene therapy in research and early trials, not from injectable proteins or supplements sold as "follistatin," which run ahead of the evidence. No follistatin therapy is broadly approved.
No — this is a research and educational reference. Follistatin-based approaches are investigational and the pathway is banned in sport.