Follistatin 344
Follistatin · FST-344 · FS-344
Follistatin 344 (FST344) is a recombinant form of the naturally occurring glycoprotein follistatin, which is a potent endogenous inhibitor of activins, myostatin, and other members of the TGF-beta superfamily. The 344 designation refers to the full-length 344-amino-acid isoform, which is the precursor form that can be processed into shorter tissue-specific variants (FST315 and FST288). Follistatin plays a critical role in regulating muscle growth, reproductive physiology, and tissue repair.
Start here. Every protocol below is ordered lowest-first. Begin at the smallest effective dose, hold about a week to assess tolerance, and step up only if needed.
How it works
Binds and neutralizes myostatin (GDF-8), activin A, and activin B with high affinity, preventing them from activating their type II receptors (ActRIIA/ActRIIB). By sequestering myostatin, follistatin removes the primary brake on skeletal muscle growth, allowing the Akt/mTOR hypertrophy pathway to proceed unchecked.
Modulates the activin-FSH axis in reproductive physiology. By binding activin, follistatin reduces FSH secretion from the anterior pituitary, which can affect gonadal function. This reproductive effect is an important consideration for off-label use.
May promote satellite cell activation and muscle regeneration by reducing TGF-beta superfamily signaling that normally inhibits myogenic differentiation. Also implicated in reducing fibrosis in damaged tissues by antagonizing activin-driven fibrotic pathways.
What to expect
Days 1-7: Circulating myostatin is being bound by exogenous follistatin. No visible or subjective muscle changes expected in the first week.
Evidence
Claims we could not support
No abstract we checked supports these for this molecule at this route. That is not the same as saying they are false — it marks where the evidence is missing.
Dose/route: 100 mcg FS344 protein SubQ daily. No checked abstract administered this regimen.
Mechanism for displayed injected protein. Human studies used AAV gene delivery into muscle; formulation mismatch blocked transfer.
Primary safety. No same-formulation, same-route human abstract established it.
Interactions & stacking
Two different questions: what is documented about running these together, and what is documented about drawing them into the same syringe. A good pharmacological partner can still have to be pinned separately.
Documented together
Check any specific pair in the Stack & Interaction Checker, which answers both questions separately. Absence of a documented conflict is not evidence of safety.
Pharmacokinetics
Estimated hours for recombinant protein (exact data limited). Rapid renal clearance expected for the unmodified protein. Gene therapy delivery achieves sustained expression lasting months to years.
SubQ (estimated)
Recombinant protein, estimated
Variable SubQ (large protein, absorption may be incomplete)
Myostatin binding effects persist while protein is circulating
Renal filtration and hepatic uptake (large protein rapidly cleared from circulation)
Storage. Store refrigerated at 2-8C. Reconstituted solution should be used within 7-14 days. Avoid repeated freeze-thaw cycles. Sensitive to degradation.
Regulatory status
Research compound only. Not approved by the FDA or any regulatory agency for injectable human use. Gene therapy variants (AAV-follistatin) are in clinical trials for muscular dystrophies. Not a controlled substance but may violate anti-doping regulations (WADA prohibited list under gene doping/growth factors).
Put it to work
Calculate, log & track
Open Follistatin 344 straight into OnePin with your vial and dose pre-filled, then let it handle the syringe math and remind you before the vial runs out.
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The guide & community
The complete Follistatin 344 walkthrough, real protocol discussion and coaching live inside the BlessUp community on Skool.
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