Follistatin 315
The circulating follistatin isoform — activin and myostatin binding, no human trials.
For research purposes only. These products are not intended to diagnose, treat, cure, or prevent any disease. By purchasing, you confirm these products will be used for legitimate research purposes.
About Follistatin 315
Follistatin 315 is the 315-amino-acid isoform of follistatin, the form that predominates in circulation, as distinct from the 344-amino-acid precursor form that binds to cell-surface heparan sulphate and stays largely tissue-associated. Both neutralise activin and myostatin by binding them directly, which is the basis of interest in follistatin for muscle mass. The practical difference is distribution: FST315 circulates while FST344 tends to remain where it is produced. Neither has been administered to humans as an injected protein. The human follistatin data that exists comes from AAV gene therapy — a completely different modality that causes sustained endogenous production, and which cannot be used to infer what injecting the protein would do.
Key Benefits
- Binds and neutralises activin and myostatin directly
- The isoform that predominates in circulation
- Well-characterised structural biology
Set a goal (top of the page) to see how Follistatin 315 scores against it, and what the better-evidenced alternatives are.
Category Ratings
How to Take
Common Side Effects
- Injection site reactions
- Joint discomfort
- Theoretical risk of unregulated tissue growth with prolonged use
- Unknown — the injected protein has no human safety data
Legal & Regulatory Status
Research use only. Not FDA-approved. Human follistatin data comes from AAV gene therapy, a different modality — it does not transfer to the injected protein.
Safety and regulatory details for FDA-approved compounds are drawn from the official product label via openFDA; clinical development status reflects ClinicalTrials.gov. This information is provided for research reference, is not endorsed by the FDA, and may not be complete or current.
Research & Sources
Sources are selected for reliability (peer-reviewed literature, openFDA, ClinicalTrials.gov) but this is a research summary, not medical advice, and may not be exhaustive.