Healing & Recovery

Follistatin 344

FS-344 · Follistatin

Follistatin-344 is a myostatin/activin-binding glycoprotein isoform. Animal myostatin biology is real. Gray-market 100–300 mcg vials are not ACE-031 (a discontinued ActRIIB fusion) and not a human muscle-wasting drug. WADA S4. Fertility/FSH caveats are part of the class, not optional fine print.

Not FDA-approved - research chemical
Reviewed by CalcMyPeptide Editorial Team
Last updated: August 2026Evidence: Low3 peer-reviewed citations
Typical research dose
100-300 mcg/day
Frequency
1× daily for 10-30 days
Half-life
Endogenous protein is hours-or-less class; SKU PK unpublished
Common vials
1 mg
CAS
80529-93-7
Molecular weight
~35–38 kDa class (glycosylation varies)

Use-case scores

0–10 against the evidence we have, not a gym ranking. Hidden domains do not apply here.

  • Muscle / recomp3.5/10

    Myostatin biology is multi-lab and animal-dramatic. Gray-market FST-344 is not that experiment. Community ceiling plus a half-step for the strength of the ligand class, still well under any gene-therapy headline.

  • Sexual / hormonal3/10

    Activin/FSH is the fertility caution, not a PCT tool. Do not score it as a hormone optimizer.

Compound card

Sequence
FST-344 (tissue-associated splice; 344 aa class)
Class
Myostatin/activin-binding glycoprotein (not ACE-031)
Formula
Glycoprotein isoform 344 (vendor sequence often unverified)
Status
Not FDA-approved · research use
Dose it
1 mg + 1 mL BAC water → 1 mg/mL · 100 mcg ≈ 10 units (U-100)
Open in calculator

How it works

Follistatin binds myostatin (GDF-8) and activins, blocking ActRIIB. Nakamura 1990 (Science, PMID 2173733) is the activin-inhibitor paper. Isoform 344 is the tissue-associated splice; 315 is the circulating form with an acidic tail. Gray-market 100–300 mcg vials are not gene therapy, not Belgian Blue cattle, and not ACE-031 (ramatercept, an ActRIIB-Fc fusion that was discontinued).

Removing a growth brake in a mouse or a myostatin-null animal is not a human hyperplasia protocol. Activin binding is why FSH/fertility shows up. WADA S4. This is not a BPC-class recovery peptide just because the catalog said recovery.

Source: PMID: 17108139

Not ACE-031, not a casual recovery peptide

ActRIIB fusion drugs are a different molecule. WADA S4. Fertility/FSH is class pharmacology.

Goal context

Myostatin is a real brake

That sentence is true. The next sentence vendors skip is that pharmacological blockade in humans has been a graveyard of safety and delivery problems. A 1 mg cake does not skip that graveyard.

315 vs 344

Localization more than ligand. See the 315 leaf. Do not buy both thinking you stacked two drugs.

Background & History

Follistatin-344 binds myostatin and activins. Nakamura 1990 is the activin-binding paper. Gray-market 100–300 mcg vials are not gene therapy, not Belgian Blue cattle, and not ACE-031 (a discontinued ActRIIB fusion). WADA S4. Fertility/FSH is class pharmacology.

Research Use Cases

  • ✓FST-344 isoform identity (vs 315)
  • ✓Not a casual recovery peptide or sport supplement

Dosing

PhaseDoseFrequencyNotes
Community research-chem (unlabeled)100–300 mcgDaily or 3× weekly SC, short cyclesForum range. Not a label. Not gene therapy.

Administration

Route / form
Subcutaneous (research). Gene-therapy IM papers are not this SKU.
Timing
Not established.
Empty stomach?
No - Food timing is not critical.

Timeline

Unknown in humans at this dose
Anecdote is not a myostatin assay. Watch reproductive labs if anyone is actually running this with a clinician.

Who it is for

Need FST-344 identity

Low

This isoform. Biology real, vial weak.

Need a legal sport supplement

Low

WADA S4. Wrong tool.

Reconstitution

VialWaterConcentrationExample dose
1 mg1.0 mL BAC1 mg/mL100 mcg = 0.10 mL = 10 units on a U-100 syringe

Change vial size or water volume? Open the reconstitution calculator.

Safety & Considerations

Research glycoprotein. Activin/FSH effects can hit fertility. Vascular and off-target TGF-β issues are why myostatin drugs keep stalling. Not for conception attempts. Contamination risk on gray-market protein is not theoretical. WADA S4.

Regulatory & Legal Status

FDA Status (US)
Research Only
WADA Status (2026)
Not Listed

Not currently on the WADA 2026 Prohibited List. Policies may change - verify before competition.

Classification

Research Chemical

US Compounding: Not eligible / not available

⚠️ This information is for educational purposes only and may not reflect the most current regulatory updates. Always verify with official FDA, WADA, and jurisdiction-specific sources before use.

Limits of current evidence

  • PMID 2173733 is activin biology, not a human 100 mcg trial.
  • Myostatin-knockout animals and follistatin gene therapy are not this vial.
  • ACE-031 / ramatercept was a different molecule and was discontinued.
  • Identity of gray-market 344 vs 315 is often unverified.

Verdict

Follistatin-344 is a real myostatin binder and a weak, high-risk research SKU. Do not expect cattle-level muscle from 100 mcg, do not confuse it with ACE-031, and do not skip the fertility warning.

Interactions & Contraindications

Activin/FSH can hit fertility. WADA S4. Gray-market protein contamination is a practical risk.

Synergies & Common Stacks

+ Follistatin 315 →

Isoforms, not two drugs. Do not buy both thinking you stacked them.

Frequently Asked Questions

Does FST-344 inhibit myostatin?▼
The protein class does. Your 1 mg vial is not a knockout mouse and not gene therapy.
Is this ACE-031?▼
No. ACE-031 was ActRIIB-Fc, discontinued. Different molecule.
344 vs 315?▼
344 is tissue-associated; 315 is circulating. Same ligand class. See the 315 leaf.
How do I reconstitute a 1 mg vial?▼
Add 1.0 mL BAC for 1 mg/mL. 100 mcg is 0.10 mL (10 units).
Fertility?▼
The name is about inhibiting follicle-stimulating signaling via activin. That is a real class caution.
Will I get Belgian Blue hypertrophy?▼
No. Those animals lack myostatin from conception. A short peptide cycle is not that genotype.
FDA-approved?▼
No. Muscle-wasting drug programs in this lane have had a hard time.
WADA?▼
S4 (hormone and metabolic modulators / myostatin inhibitors). Not a recovery loophole.

References

  1. Nakamura T, Takio K, Eto Y, Shibai H, Titani K, Sugino H “Activin-binding protein from rat ovary is follistatin.” Science (1990). PMID: 2106159
  2. Lee SJ et al. “Regulation of muscle mass by follistatin and activins.” Mol Endocrinol / related myostatin-follistatin lineage (2010). PMID: 20943755
  3. Haidet AM, et al. “Follistatin administration stimulates muscle growth in mice.” J Clin Invest (2008). PMID: 18769635

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