What is the dosing range for Follistatin 344?

Follistatin 344 is typically dosed at 50mcg (low), 100mcg (moderate), or 200mcg (high) mcg, administered Once daily or every other day for 10–30 day cycles. These ranges are aggregated from preclinical research and community protocols — not medical dosing guidance.

What are the reported side effects of Follistatin 344?

Reported side effects of Follistatin 344 include: Potential FSH suppression (reproductive effects in females — may affect menstrual cycle), Accelerated hair follicle cycling (Wnt pathway involvement — theoretical hair loss concern at high doses), Joint discomfort with rapid muscle tissue growth, Limited long-term human safety data, Unknown interaction with cancer biology (activin inhibition has mixed effects on tumor biology).

Performance

Follistatin 344

Also known as: FST-344, Follistatin isoform 344, FST

Follistatin 344 is a research compound not approved for human use. For informational purposes only.

📚 Content aggregated from:3 peer-reviewed sources·r/Peptides community·PubMed / NCBI

Overview

Follistatin 344 is a 344-amino acid isoform of follistatin — an endogenous glycoprotein that functions primarily as a myostatin and activin inhibitor. Myostatin (GDF-8) is the body's primary muscle growth suppressor; follistatin binds and neutralizes it with high affinity, removing this brake on muscle protein synthesis. Research and animal data show dramatic increases in muscle fiber size and strength when follistatin is elevated or myostatin is inhibited.

Research Summary

Follistatin's muscle effects were dramatically illustrated when mice and cattle with follistatin overexpression or myostatin knockouts developed 2–3x normal muscle mass. Human follistatin gene therapy trials (AAV-mediated) are ongoing for Becker Muscular Dystrophy, showing sustained myostatin inhibition and improved muscle function over years from a single injection. Follistatin also inhibits activin A and B (involved in muscle wasting during illness), FSH secretion (reproductive effects), and inflammatory cytokines. The 344 isoform has an extended heparin-binding domain that increases tissue retention compared to the shorter FST-288 isoform.

Dosing Range

low

50mcg

moderate

100mcg

high

200mcg

Units: mcg · Frequency: Once daily or every other day for 10–30 day cycles

Dosing ranges are aggregated from preclinical research and community protocols. Not medical dosing guidance.

Administration Routes

Subcutaneous injectionIntramuscular injection (into target muscle — local effect hypothesis)

Reconstitution Notes

Reconstitute with bacteriostatic water to 1mg/mL. Highly sensitive to heat and agitation — reconstitute gently (do not vortex), store at 4°C, use within 14 days. Some protocols use intramuscular injection into the target muscle to exploit local myostatin inhibition, though systemic effects occur regardless of route.

Step-by-step reconstitution guide →

Supplies you'll need

Insulin Syringes (U-100)Reconstitution Needles Lambda BAC Water Alcohol Prep Pads

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Reported Side Effects

Potential FSH suppression (reproductive effects in females — may affect menstrual cycle)
Accelerated hair follicle cycling (Wnt pathway involvement — theoretical hair loss concern at high doses)
Joint discomfort with rapid muscle tissue growth
Limited long-term human safety data
Unknown interaction with cancer biology (activin inhibition has mixed effects on tumor biology)

Research Papers

3 peer-reviewed sources

Inhibition of myostatin in mice increases skeletal muscle mass

Nature1997

Gene therapy for muscle disease using AAV-follistatin

Science Translational Medicine2015

Follistatin 344 vs 288 isoform — tissue distribution and myostatin inhibition potency

Journal of Biological Chemistry2008

Community Experiences

Aggregated from public forums. Anecdotal — not clinical evidence.

r/Peptides

Community experience with follistatin-344 — dosing protocols, cycle lengths, and muscle hypertrophy observations.

View original thread

r/bodybuilding

Bodybuilding community discussions on myostatin inhibitors including follistatin 344.

View original thread

Overview

Myostatin — a TGF-β family member — exists for one reason: to limit muscle growth. It's an evolutionary brake that prevents muscle from consuming excessive energy resources. Follistatin removes this brake by binding myostatin with high affinity, preventing it from signaling. The result in animal models is muscle hypertrophy that defies normal physiological limits.

The Myostatin System

Myostatin (GDF-8) is produced primarily by skeletal muscle and acts in an autocrine/paracrine feedback loop:

Muscle grows → produces more myostatin
Myostatin activates ActRIIB receptor on muscle stem cells (satellite cells)
Signaling suppresses satellite cell activation and protein synthesis
Muscle growth is limited

Follistatin breaks this loop by binding myostatin before it reaches ActRIIB.

The Myostatin Knockout Effect

The clearest evidence for myostatin inhibition's muscle effects comes from genetic models:

Myostatin knockout mice: 2–3x normal muscle mass, dramatically reduced fat
Whippet dogs with myostatin mutation: Visibly "double-muscled" phenotype
Human child with myostatin mutation: Developed extraordinary muscle mass by age 4 with no adverse effects
Belgian Blue cattle: Breed with natural myostatin mutation — 100% more muscle than standard cattle

Follistatin overexpression produces similar results to myostatin knockout.

FST-344 vs FST-288

Two main isoforms exist:

FST-344: Extended C-terminal domain with heparin-binding sequence → stays bound to extracellular matrix, more localized/sustained effect
FST-288: Shorter, more systemic distribution

FST-344 is preferred for muscle applications due to tissue retention; FST-288 is preferred in reproductive biology research (less FSH suppression).

Practical Considerations

Short cycles (10–30 days) are typically used because:

The effect is potent enough that extended cycles aren't needed
Allows the activin/FSH axis to recover
Long-term myostatin suppression effects on tendon/joint adaptation are unknown

Intramuscular injection into a target muscle is used by some researchers to exploit the local tissue-retention property of FST-344 — the heparin-binding domain keeps it concentrated near the injection site.