Most available support is preclinical, mechanistic or anecdotal. Human efficacy and long-term safety are not established.
Overview
Follistatin is a naturally occurring protein that binds and inhibits myostatin (a limiter of muscle growth). It is heavily discussed in muscle-growth contexts, including gene-therapy research.
How It's Thought to Work
By neutralizing myostatin and related factors, follistatin can remove a brake on muscle growth in animal models.
What the Research Says
Most striking results are from animal and gene-therapy studies; human evidence for injectable 'follistatin' products is minimal and their real content is often uncertain.
Key studies to start with
FSTL1 promotes M2 polarization of macrophages via the DIP2A-Smad2/3 Axis in gastric cancer
Journal of translational medicine · 2026 Aug 21
PubMedSecreted Frizzled-Related Protein 2 (SFRP2) Induces Follistatin-Like 1 (FSTL1) to Regulate Dihydrotestosterone (DHT)-Induced Dermal Papilla Cell Mitochondrial Dysfunction and Senescence
Aging cell · 2026 Sep
Regulatory & Legal Status
Not FDA-approved. Sold as a research chemical; product authenticity is a major concern. Prohibited in sport by WADA.
Safety Considerations
Little to no human safety data; unregulated and often misrepresented products. Consult a qualified clinician.