Head to head
Follistatin against Myostatin
The brake and the protein that releases it. Knocking out myostatin doubles muscle in a mouse, which launched the field, and in primates the dominant brake turns out to be a different protein, which is why the human results have been smaller than the mouse images suggest.
Column A
FollistatinFollistatin (myostatin/activin antagonist)
A natural protein that blocks myostatin and activin, studied largely through gene therapy for muscle growth and muscular dystrophy.
Column B
MyostatinMyostatin (growth/differentiation factor 8)
The brake on muscle growth. Knock it out in a mouse and you get a mouse twice as muscular, which launched a field. In primates the dominant brake turns out to be a different protein.
Side by side, on the facts we can check
| Attribute | Follistatin | Myostatin |
|---|---|---|
| Category | Muscle & Performance | Muscle & Performance |
| FDA status | Not FDA-approved; investigational (gene therapy) | Myostatin is an endogenous protein, not a drug. Drugs targeting the pathway are investigational; apitegromab has phase 3 data in spinal muscular atrophy. |
| Half-life | Short (protein) | Circulates as a latent complex; no single agreed circulating half-life is asserted here. |
| Molecular weight | ~35,000 Da | Precursor 375 amino acids, 42,750 Da. Mature signalling domain is residues 267 to 375, 109 amino acids, circulating as a dimer (UniProt O14793). |
| Mechanism | Sequesters myostatin and activin, releasing their inhibition of muscle growth and promoting muscle fiber size. | Circulates as a latent disulfide-linked dimer held inactive by its own propeptide. Once activated it signals through activin type II receptors, principally ActRIIB, with type I receptors ALK4 and ALK5, through SMAD2 and SMAD3, to suppress muscle protein synthesis and satellite cell activity. Activin A signals through the same type II receptors, which is the whole reason receptor-level blockade and ligand-level blockade behave so differently. |
| Human studies cited | 2 | 4 |
| Legal status, US | Not approved; research use only | Not a drug; endogenous hormone and research infusion peptide |
Frequently asked questions
What is the difference between Follistatin and Myostatin?
Follistatin: A natural protein that blocks myostatin and activin, studied largely through gene therapy for muscle growth and muscular dystrophy. Myostatin: The brake on muscle growth. Knock it out in a mouse and you get a mouse twice as muscular, which launched a field. In primates the dominant brake turns out to be a different protein.
Which has stronger research evidence, Follistatin or Myostatin?
This database does not grade compounds. It counts what was run in people: 2 of the 4 studies cited on the Follistatin profile were human work, against 4 of 6 for Myostatin. Those counts are of our own citation lists and understate any larger literature, and neither is a recommendation.
Are Follistatin and Myostatin FDA-approved?
Follistatin: Not FDA-approved; investigational (gene therapy). Myostatin: Myostatin is an endogenous protein, not a drug. Drugs targeting the pathway are investigational; apitegromab has phase 3 data in spinal muscular atrophy..
Reviewed Sep 2026. This page sets two published records side by side. It is educational, it is not medical advice, and it contains no dosing protocols or recommendations for personal use.