data + articles · 3 listed
newest 2016spec sheet9 rows
Follistatin 315 is the main circulating (blood-borne) isoform of follistatin, a naturally occurring protein 315 amino acids long that binds and neutralizes members of the TGF-beta family such as activin and myostatin. Because myostatin is a brake on muscle growth, follistatin's ability to soak it up has made this isoform a subject of muscle-growth and body-composition research. It is a research protein, not an established supplement.
- Neutralizes myostatin
- Studied for increased muscle mass
- Modulates activin signaling
- Experimental with poorly defined risks
- Broad effects on TGF-beta signaling
Mechanism
Follistatin acts as a high-affinity binding trap for activin and, importantly, for myostatin (also called GDF-8), the signaling protein that normally limits skeletal muscle size; by wrapping up myostatin, follistatin prevents it from engaging its activin type II receptors and blocks the downstream Smad signaling that restrains muscle. The 315 isoform is the soluble form that circulates in blood, distinguished from the 288 isoform that binds more tightly to cell-surface heparan sulfate; the 315 form has lower cell-surface affinity and so acts more as a circulating buffer. Blocking myostatin and activin this way is the basis for the observed increases in muscle mass in animal models.
receptor fingerprint
Myostatin (GDF-8)binding and neutralization
Activinbinding and neutralization
Activin type II receptor signalingindirect blockade (ligand trapping)
Dosingtypical ranges, not medical advice
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Safetyrisks and cautions, not medical advice
Follistatin-based muscle-growth approaches are experimental, and interfering with the activin and myostatin system has broad effects beyond muscle, including on reproduction, wound healing, and possibly tumor-related signaling, so the risks are not well defined in humans. Research-grade proteins also raise purity and sterility concerns, and unsupervised use of gene- or protein-based myostatin inhibitors is a serious undertaking. Not medical advice.
Subjective profileweighing the evidence above
Experimental, and more so than the muscle-growth marketing suggests. Blocking myostatin and activin reaches into reproduction, wound healing and possibly tumor signaling, none of it mapped in humans, and research-grade protein adds purity and sterility problems on top.
Resources
This entry is here for reference.
Research
- 2006first citedBiological activity of follistatin isoforms and follistatin-like-3 is dependent on differential…
- 2016most recentINVITED REVIEW: Inhibitors of myostatin as methods of enhancing muscle growth and development
- 1.Biological activity of follistatin isoforms and follistatin-like-3 is dependent on differential cell surface binding and specificity for activin, myostatin, and bone morphogenetic proteins
- 2.INVITED REVIEW: Inhibitors of myostatin as methods of enhancing muscle growth and development
- 3.Follistatin and follistatin like-3 differentially regulate adiposity and glucose homeostasis
3 listed here; entry last updated July 2026
Reviews
My notesprivate to this device
FAQ
How is follistatin 315 different from follistatin 288?
Both trap activin and myostatin, but the 315 form is the soluble circulating isoform with lower cell-surface binding, while 288 sticks more tightly to cell surfaces.
Does it really build muscle?
By neutralizing myostatin it can increase muscle mass in animal models, but human evidence is limited and the approach is experimental.
Is it safe to use for muscle growth?
The activin and myostatin system affects far more than muscle, so the risks are not well defined and unsupervised use is a serious undertaking. This is not medical advice.
Adverse effects
- Experimental with poorly defined risks
- Broad effects on TGF-beta signaling
Notes and cautions
- Research-grade quality concerns