Follistatin 315
Also known as: FST-315 · Follistatin isoform 315
The circulating 315-amino-acid isoform of the natural protein follistatin, studied for its ability to bind and neutralize myostatin and activin, potentially favoring muscle growth.
Follistatin 315 at a glance
| Name | Follistatin 315 |
|---|---|
| Also known as | FST-315, Follistatin isoform 315 |
| Category | Growth & muscle |
| Type | Peptide |
| Sequence | 315-residue circulating isoform of the follistatin protein |
| Typical dose | ~100 mcg per day |
| Frequency | Often cited over short multi-day cycles in research discussions |
| Route | Subcutaneous injection (research) |
| Half-life | Not firmly established; the 315 isoform is described as more systemically distributed than the 288 form. |
Overview
Follistatin 315 is the main blood-borne isoform of follistatin, a naturally occurring protein that binds and inhibits members of the TGF-beta family, including myostatin and activin. Because myostatin limits muscle growth, research has examined follistatin as a way to release that brake. The 315 isoform has lower affinity for cell-surface heparan sulfate than the 288 isoform, giving it a more systemic distribution. It is an investigational protein and is not approved for human use.
How it’s thought to work
- Binds and neutralizes myostatin, reducing its brake on muscle growth.
- Also binds activin and other TGF-beta family ligands.
- The 315 isoform circulates more systemically due to lower heparan-sulfate binding.
- Net effect in research models is a shift toward muscle growth signaling.
Researched uses
- Myostatin-inhibition and muscle-growth research
- Studies of follistatin isoform distribution and activity
- Investigating activin and TGF-beta pathway regulation
Commonly cited protocol
| Typical dose | ~100 mcg per day |
|---|---|
| Frequency | Often cited over short multi-day cycles in research discussions |
| Route | Subcutaneous injection (research) |
| Notes | Dosing figures come from research contexts, not established human protocols. |
Reconstitution
Commonly supplied as a 1 mg lyophilized vial. Reconstituting 1 mg with 1 mL of bacteriostatic water gives 1 mg/mL, so a 100 mcg dose is about 10 units on a U-100 syringe.
Follistatin 315 dosage calculator
The calculator below is pre-filled with Follistatin 315’s commonly cited vial size and dose. Adjust the vial amount, bacteriostatic water, or dose to match your own vial — it will show the exact insulin-syringe units to draw, the concentration, and how many doses the vial holds.
Add 1 mL of bacteriostatic water to your 1 mg vial. That gives you about 10 doses of 100 mcg. For each dose, draw 10 units into a 100-unit insulin syringe.
See the full Follistatin 315 dosing chart (units for every dose & water amount), or open the full peptide calculator →
Cautions
- A research protein not approved by the FDA for human use; prohibited in sport.
- Human safety and efficacy data are very limited.
- Broad TGF-beta pathway inhibition raises theoretical off-target concerns.
- Research-grade purity varies by source.
Follistatin 315 FAQ
What is Follistatin 315?
The circulating 315-amino-acid isoform of the natural protein follistatin, studied for its ability to bind and neutralize myostatin and activin, potentially favoring muscle growth.
How does Follistatin 315 work?
Binds and neutralizes myostatin, reducing its brake on muscle growth. Also binds activin and other TGF-beta family ligands. The 315 isoform circulates more systemically due to lower heparan-sulfate binding. Net effect in research models is a shift toward muscle growth signaling.
What is Follistatin 315 used for?
Myostatin-inhibition and muscle-growth research; Studies of follistatin isoform distribution and activity; Investigating activin and TGF-beta pathway regulation.
What is a typical Follistatin 315 dose?
~100 mcg per day, Often cited over short multi-day cycles in research discussions, Subcutaneous injection (research). This is a commonly cited figure for context only, not medical advice.
How do you reconstitute Follistatin 315?
Commonly supplied as a 1 mg lyophilized vial. Reconstituting 1 mg with 1 mL of bacteriostatic water gives 1 mg/mL, so a 100 mcg dose is about 10 units on a U-100 syringe.
What is the half-life of Follistatin 315?
Not firmly established; the 315 isoform is described as more systemically distributed than the 288 form.