Overview

Myostatin inhibition produces the double-muscled cattle phenotype, and follistatin is one way to achieve it. The gene therapy work in muscular dystrophy is legitimate. The injectable version sold to bodybuilders is not the same intervention and has essentially no supporting data.

Not approved for human use anywhereNo approval anywhere for human use. Sold under research-use labelling. Not approved for human use.

At a glance

Regulatory status	Not approved. Follistatin gene therapy has been studied in muscular dystrophy trials; injectable recombinant follistatin has not been developed for human use.
Drug class	Recombinant follistatin isoform — an activin and myostatin-binding glycoprotein
Route	Subcutaneous (research); gene therapy in trials
Half-life	Very short as a protein — minutes to hours
Evidence rating	1/5 Minimal Evidence rating 1 out of 5: Minimal Animal or laboratory data only. No human efficacy evidence.
Studied in	AAV-delivered follistatin gene therapy phase 1/2 trials in Becker muscular dystrophy and inclusion body myositis; extensive animal work. No trials of injectable recombinant follistatin.

How it works

Binds and neutralises myostatin (GDF-8) and activins, removing the brake on skeletal muscle growth. Activin signalling also regulates reproduction, inflammation and tissue fibrosis, so blocking it has effects well beyond muscle.

Evidence base

Rated 1 of 5 — Minimal. Animal or laboratory data only. No human efficacy evidence.

Legitimate gene therapy research; the injectable consumer product is unrelated to it.

Benefits & potential uses

Bars indicate how well each claim is supported: three = strong human evidence, two = moderate, one = preliminary or preclinical.

Dramatic muscle growth in animal models Preliminary

Follistatin overexpression produces substantial and sustained muscle hypertrophy in mice and non-human primates.
Gene therapy signals in muscular dystrophy Preliminary

Small early-phase trials reported improved 6-minute walk distance and muscle histology.
Antifibrotic activity Preliminary

Activin blockade reduces fibrosis in preclinical models of muscle and organ disease.

Risks, cons & cautions

Bars indicate seriousness: three = serious or common, two = moderate, one = minor.

Injectable form is unstudied in humans Serious

The trial evidence is for gene therapy — a completely different intervention with different pharmacology.
Activin blockade affects multiple systems Serious

Reproductive function, inflammatory regulation and tissue repair all depend on activin signalling.
Tendon-muscle mismatch injury Moderate evidence

Muscle hypertrophy outpacing tendon adaptation is a documented injury mechanism in myostatin-inhibited animals.
Cardiac muscle effects unknown Serious

Myostatin is expressed in cardiac tissue; consequences of chronic inhibition in the heart are not characterised.
Very poor bioavailability Moderate evidence

Rapid clearance makes injected recombinant follistatin unlikely to achieve meaningful sustained effect regardless.
Extremely expensive and frequently counterfeit Serious

Genuine recombinant follistatin is costly; grey-market products are often not what they claim.

Who should avoid it

All non-trial human use
Cancer history — activin signalling is involved in tumour suppression

If used under medical supervision, monitor

Not applicable

Commonly confused with

These mix-ups cause real harm — two products sold under one name, or two molecules whose effects run in opposite directions.

GDF-11 Research Use Only Evidence 1/5

Follistatin blocks myostatin and activins to increase muscle. GDF-11 is myostatin-like and may reduce it. They are sold adjacently but may act in opposite directions.

Compare side by side

Regulatory & legal status

Not approved for human use.

Infographic

Follistatin-344 — benefits & risks at a glance Download SVG

Where to read further

We link to live literature searches rather than a frozen citation list, so you always see current results — including anything published after our last review.

musclemyostatingene therapyresearch chemicalhigh risk

Related peptides in Bone, Muscle & Other

Terms used on this page

Myostatin: Myostatin is a muscle-secreted member of the TGF-beta family that acts as a brake on muscle growth, and blocking it enlarges muscle far more reliably than it improves function.
Muscle Hypertrophy: Muscle hypertrophy is an increase in the cross-sectional area of existing muscle fibres through net accumulation of contractile protein, rather than an increase in fibre number.
Fibrosis: Fibrosis is the accumulation of excess extracellular matrix that replaces functional tissue, representing repair that has failed to resolve rather than a separate disease process.
Preclinical Study and Animal Model: Preclinical studies are the laboratory, cell and animal experiments done before any human exposure, establishing mechanism, target engagement and the toxicology package that permits a first trial.
Tendon Structure: Tendon is a hierarchical collagen composite transmitting muscle force to bone, built from fibrils and fascicles held in a sliding matrix and populated sparsely by tenocytes.

This page is educational information, not medical advice. It cannot account for your medical history, medications, or risk factors. Do not start, stop or change any treatment based on it. Speak to a qualified healthcare professional who knows your case.