SEINE BIO · SCIENCE LIBRARY
Follistatin / FST-344
Follistatin is a protein involved in activin and myostatin-related signaling. Different isoforms and delivery approaches appear in research.
Research compoundA closer look at the research, the uncertainties and the questions worth asking.
THE FULL READING GUIDE · UPDATED OCTOBER 7, 2026
Inside the science of Follistatin / FST-344.
Educational purpose only. Not medical advice. Consult licensed provider. Obtain from authorized compounding pharmacies only.
Compounding is appropriate only when lawful for the specific substance and patient; some substances may be unavailable. Finished FDA-approved medicines may also be dispensed by licensed non-compounding pharmacies.
Overview
Follistatin is a regulatory protein involved in activin and myostatin signaling. FST-344 refers to a particular follistatin isoform, not a standardized consumer muscle-building medicine. The most relevant human evidence here concerns experimental gene transfer in a serious muscle disease. Understanding exactly what was studied prevents a familiar research name from becoming an unsupported promise about a vial.
Community Use
Fitness discussions often connect follistatin with muscle size or myostatin inhibition. Those descriptions leave an important identity question unanswered: is the discussion about a gene construct, a purified protein, or a different isoform? No matching FST-344 profile was found in the two requested community catalogs during this review. A missing reference should remain a gap, not be filled with an invented protocol.
Doses, Durations & Cycles
Informal biohacking protocols and published regimens. Attributed website reports for education, not medical recommendations. Multiple publications document circulation; they do not establish a safe dose or validate a cycle.
| Route / formulation | Dose / reported phases | Frequency | Duration / break | Notes and source |
|---|---|---|---|---|
| Subcutaneous | 100–200 mcg per administration | Daily or every other day for the short course; separate pattern: twice weekly | Short course: 10–30 days; separate twice-weekly pattern: 8–12 weeks; notes also describe seven daily days before twice-weekly maintenance Break: 3–4 weeks in narrative notes | Published informal biohacking claim PeptaBase |
| Subcutaneous | Conservative: 100 mcg; standard: 100–200 mcg; separate advanced row: 200–300 mcg | Once daily | Conservative: 10–20 days; standard: 20–30 days; advanced row: 10–20 days Break: Conservative and standard: 3–4 weeks; advanced row: 4 weeks | Published informal biohacking claim PeptidesExplorer |
Important context: Human FS344 research used AAV1-mediated gene delivery into quadriceps. That vector/transgene treatment is not a microgram dose of commercially sold injectable protein. Follistatin isoform and product identity must be stated; gene-therapy results must not be presented as validation of these vial schedules.
Additional sources: Mendell et al., Follistatin Gene Therapy for Sporadic Inclusion Body Myositis Improves Functional Outcomes, Molecular Therapy (2017). Consult the linked record for its exact formulation, population and methods.
Sources checked October 7, 2026. Educational listing does not establish prescribing approval or availability through Seine Bio.
There is no validated human wellness dose or consumer cycle for an injectable FST-344 product. Gene-therapy doses are expressed in vector-genome units and cannot be converted into milligrams of an unrelated protein preparation. A protocol chart should therefore identify the experimental product and study context, rather than offer a muscle-building schedule.
Research Findings
A phase 1/2a study enrolled six people with Becker muscular dystrophy and delivered an AAV1 follistatin gene construct to quadriceps muscles. This was a small, disease-specific human investigation, not a trial of retail follistatin injections in healthy athletes. Human gene-transfer study.
U.S. Approval & Access
This source review does not establish an FDA-approved FST-344 injectable product for fitness, recovery, or age management. Approval of any future gene therapy would apply to that particular product and indication. A research-only label, prescription request, or pharmacy name cannot independently establish a lawful patient-care route.
What It Does in the Body
Follistatin binds signaling proteins rather than simply replacing testosterone or growth hormone. Its interaction with activin-family pathways helps explain the interest in muscle biology. It also explains why a narrow focus on muscle size is incomplete: changing a regulatory pathway may affect more than the outcome that an athlete hopes to improve. Reliable onset, peak clinical benefit, and duration for a retail FST-344 preparation are unknown; gene-expression timing is not an injectable-protein timetable.
Benefits & Reported Experiences
Walking performance improved in some participants in the small gene-transfer study, while others did not improve. This is a signal worth investigating, not evidence that all users build stronger muscle or recover faster. Healthy-person outcomes, injectable-protein outcomes, and long-term functional benefits require their own studies.
Side Effects & Risks
The small trial reported no adverse effects attributable to its intervention during the reported observation. That finding cannot establish safety for a different product, repeated exposure, or a much larger population. Unknown reproductive, immune, and systemic effects deserve particular attention when an online description presents a pathway intervention as a simple supplement.
Delivery Options
The human study used specialist gene delivery into selected muscles. That route does not validate subcutaneous or intramuscular self-use of research material. Route, delivery platform, and duration of expression are part of the intervention, not interchangeable packaging choices. This profile provides no injection instructions or powder-handling guidance.
Product Quality & Storage
A useful identity review asks for the exact isoform, formulation, manufacturing controls, and evidence connecting that product to human care. A certificate describing chemical purity does not answer questions about potency, immune reactions, or clinical effectiveness. For gene constructs, laboratory and regulatory oversight are fundamentally different from ordinary dispensing. There are no validated consumer storage directions for retail FST-344 here; gene-transfer study-product handling belongs to the research team.
Combinations & Interactions
Combining follistatin with anabolic steroids or growth-hormone secretagogues has not been established as a safe or effective wellness program by the cited study. More muscle-related mechanisms do not prove additive benefit. Combination claims should identify a genuine human combination study rather than collect separate pathway diagrams.
Talking With Your Provider
If muscle weakness, loss of function, or poor recovery is your concern, start with the cause and an assessment of measurable function. Bring the exact product or article you encountered to a licensed clinician. A consultation can distinguish an investigational concept from appropriate rehabilitation, nutrition, diagnostic testing, or established care.
Educational purpose only. Not medical advice. Consult licensed provider. Obtain from authorized compounding pharmacies only.
Compounding is appropriate only when lawful for the specific substance and patient; some substances may be unavailable. Finished FDA-approved medicines may also be dispensed by licensed non-compounding pharmacies.
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