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evidence · mechanism · dose
Experimental/Anabolic / Growth FactorResearch peptide

Follistatin-344

Natural myostatin-binding protein that releases the brake on muscle hypertrophy.

Educational explainer of a research peptide. Profiles in this section deliberately omit clinical-trial citations, dosing protocols, and purchase links. Not FDA-approved as a supplement; not a recommendation to use.

Overview

Follistatin-344 is an isoform of follistatin, a glycoprotein that binds and inactivates myostatin (GDF-8) and activin A, both of which limit muscle growth.

Source
  • Recombinant expression
Forms
  • Subcutaneous or intramuscular injection (research)

Mechanism of action

Sequesters myostatin and activin in circulation, removing inhibitory tone on muscle growth and influencing FSH dynamics.

Pathways
  • · Myostatin (GDF-8) neutralization
  • · Activin A sequestration
Hormones
  • · FSH (indirect via activin)

How it acts on the body

Myostatin is the dominant brake on muscle growth — animals lacking it develop hugely hypertrophic muscles. Follistatin binds myostatin tightly and removes it from circulation, releasing that brake. The 344 isoform circulates systemically rather than staying at the ovary, which is the relevant property for muscle research.

Because follistatin also neutralizes activin A, sustained dosing has downstream effects on the FSH axis and on tissues sensitive to activin signaling (liver, ovary, pancreas). This is the basis for concerns about chronic use beyond the muscle compartment.

Hormonal & endocrine impact

How this peptide is reported to shift specific hormones and signaling molecules. Directionality reflects research literature and preclinical models, not clinical prescribing data.

Projected hormonal trajectory
Illustrative curves derived from reported direction of effect. Not measured patient data.

Curves are schematic shapes (sigmoid for increases/decreases, damped oscillation for modulation/stabilization) anchored to a 100% baseline. They communicate direction and tempo of change reported in research literature — not absolute hormone concentrations.

Myostatin (free)Decreases
Sequestered and inactivated.
Activin ADecreases
Also bound and neutralized.
FSHModulates
Activin/follistatin balance shifts FSH dynamics over time.

Effects on the body

Inhibits
Myostatin signaling
Supports
Muscle hypertrophy capacity

Organ system effects

Skeletal Muscle

Removes the dominant negative regulator of growth.

Endocrine

Activin-FSH axis effects with chronic dosing.

Reported effects

Drawn from preclinical research, anecdote, and small-scale clinical observation. No evidence grades are assigned — most peptides on this page lack rigorous human trials.

  • Theoretical hypertrophy support
  • Studied in muscular-dystrophy research

Potential side effects

Common
  • · Injection-site soreness
Rare
  • · Headache
Serious
  • · Off-target effects on reproductive and hepatic activin signaling

Drug interactions

No notable interactions reported.

Pairing context

Often combined with
  • Progressive resistance training
    Removing the brake matters only if a growth signal is present.
Avoid combining with
  • Reproductive or hormonal disorders
    Activin axis disruption is poorly characterized.
Important. Research peptides described here are not FDA-approved supplements. Supplement Scholar does not endorse, recommend, or link to any source for purchase. Consult a qualified clinician before considering any peptide therapy.