Follistatin vs Myostatin
Written by Aaron CuhaReviewed Sep 2026
The short answer
The brake on muscle growth, and the protein that releases it. Knocking out myostatin doubles muscle in a mouse, which launched the field. In monkeys and apes the main brake turns out to be a different protein. That is why human results have been smaller than the mouse pictures suggest.
- Follistatin people
- 12
- Follistatin nulls
- 0
- Myostatin people
- 188
- Myostatin nulls
- 1
Dose
No human dose established
Amounts that were given in studies sit in Human evidence on this page. None of them is a personal dose.
2 completed trials, 12 people given it
Dose
No human dose established
Amounts that were given in studies sit in Human evidence on this page. None of them is a personal dose.
3 completed trials, 188 people given it
First-hand reports are counted on each profile and never added together. This page sets two published records side by side. It does not pick a winner.
Column A
FollistatinFollistatin (myostatin/activin antagonist)
A natural protein that blocks myostatin and activin, two brakes on muscle growth. It is studied mostly as gene therapy for muscle wasting diseases.
Column B
MyostatinMyostatin (growth/differentiation factor 8)
Myostatin is the body's brake on muscle growth. Mice bred without it grew two to three times more muscle, which started a whole field. In monkeys, though, a different protein turns out to be the main brake.
Side by side, on the facts we can check
| What we compare | Follistatin | Myostatin |
|---|---|---|
| Category | Muscle & Performance | Muscle & Performance |
| FDA status | Not FDA-approved; investigational (gene therapy) | Myostatin is a protein the body makes, not a drug. Drugs that target it are investigational. Apitegromab has results from final-stage studies 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). |
| How it works | It soaks up myostatin and activin, which normally hold back muscle growth. With those brakes off, muscle fibres grow bigger. | Myostatin travels in the blood in a locked, inactive form. Once unlocked, it docks on a receptor on muscle cells, mainly one called ActRIIB. That sends a signal inside the cell that slows muscle building and keeps muscle repair cells quiet. Activin A uses the same receptor. That is why blocking the receptor and blocking myostatin alone behave so differently. |
| Studies in people | 2 | 4 |
| Evidence | Limited: 2 completed trials, 12 people given it | Moderate: 3 completed trials, 188 people given it |
| Legal status, US | Not approved; research use only | Not a drug; a natural body hormone, given only by drip in research |
Frequently asked questions
What is the difference between Follistatin and Myostatin?
Follistatin: A natural protein that blocks myostatin and activin, two brakes on muscle growth. It is studied mostly as gene therapy for muscle wasting diseases. Myostatin: Myostatin is the body's brake on muscle growth. Mice bred without it grew two to three times more muscle, which started a whole field. In monkeys, though, a different protein turns out to be the main brake.
Which has stronger research evidence, Follistatin or Myostatin?
Each compound gets a band worked out from facts we counted, with the math shown. Follistatin is Limited (2 completed trials, 12 people given it). Myostatin is Moderate (3 completed trials, 188 people given it). That counts how much has been done in people. It does not rate whether either one works, and neither one is called the winner.
Are Follistatin and Myostatin FDA-approved?
Follistatin: Not FDA-approved; investigational (gene therapy). Myostatin: Myostatin is a protein the body makes, not a drug. Drugs that target it are investigational. Apitegromab has results from final-stage studies in spinal muscular atrophy..
Reviewed Sep 2026. This page puts two published records side by side. It is for learning, and it is not medical advice. When this site shows a dose, it is the dose a trial or a clinic actually used, or what people say they did, with the source attached. None of it tells you what to take.