Follistatin 344
Also known as FST-344, FS344
Follistatin 344 is one of two naturally occurring isoforms of follistatin, a glycoprotein that binds and neutralizes activin and other TGF-beta superfamily members, most notably myostatin, a primary negative regulator of muscle mass. It gained attention following animal studies in which overexpression produced pronounced increases in skeletal muscle size. As a synthetic research peptide, it is studied for its potential to counteract myostatin-driven limits on muscle growth. Human data are sparse, and most supporting evidence comes from cell culture and animal gene-therapy models rather than peptide-dosing trials in people.
Reported benefits
- Proposed reduction of myostatin-mediated suppression of muscle growth
- Suggested support for satellite cell activation and muscle repair
- Interest as an adjunct in research settings focused on preserving lean mass
- Broader activin inhibition that may affect other TGF-beta-regulated tissues
How it works
Follistatin 344 binds directly to myostatin (GDF-8) and related activins, preventing them from engaging the activin type IIB receptor and blocking the downstream Smad2/3 signaling that normally suppresses muscle protein synthesis and satellite cell activity. Because the 344 isoform carries a heparin-binding domain, it associates more readily with cell-surface proteoglycans, concentrating its activity near tissue surfaces. This is proposed to shift muscle growth signaling toward hypertrophy.
Dosing ranges
| Tier | Dose | Frequency |
|---|---|---|
| Low | 100 mcg | once daily |
| Moderate | 200 mcg | once daily |
| High | 300 mcg | once daily |
Estimate your dose
Dose estimator
Educational estimate for Follistatin 344, scaled to body size. Not medical advice.
Read before using
This tool produces a rough, educational estimate by scaling commonly-published research ranges to lean body mass. It is not a prescription, medical advice, or a substitute for a licensed clinician. Most peptides use fixed dosing, not weight-based dosing. Individual needs vary. You are solely responsible for how you use this information.
Mixing & syringe units
Target dose follows the estimate above. Change it there, or edit it directly below.
Reconstitution calculator
How much water to add and how many insulin-syringe units to draw for Follistatin 344. Educational only.
Draw to this mark
4units
= 0.04 mL for a 200 mcg dose
Concentration
5,000 mcg/mL
Doses per vial
50
A U-100 syringe reads 100 units per mL. This is a reconstitution math helper only, not a prescription or dosing advice. Verify every calculation and consult a qualified healthcare provider.
Possible side effects
Stacking notes
Sometimes discussed alongside IGF-1 analogs in research contexts aiming to combine myostatin inhibition with direct anabolic signaling; no established human data support or refute such combinations.
Common protocols
Common questions
What is Follistatin 344 used for?
Follistatin 344 is one of two naturally occurring isoforms of follistatin, a glycoprotein that binds and neutralizes activin and other TGF-beta superfamily members, most notably myostatin, a primary negative regulator of muscle mass. It gained attention following animal studies in which overexpression produced pronounced increases in skeletal muscle size. As a synthetic research peptide, it is studied for its potential to counteract myostatin-driven limits on muscle growth. Human data are sparse, and most supporting evidence comes from cell culture and animal gene-therapy models rather than peptide-dosing trials in people. Reported benefits include proposed reduction of myostatin-mediated suppression of muscle growth, suggested support for satellite cell activation and muscle repair, interest as an adjunct in research settings focused on preserving lean mass.
What is a typical Follistatin 344 dose?
Reported ranges run 100-300 mcg. A low protocol is 100 mcg once daily, and a high protocol is 300 mcg once daily. This is reference information, not a dosing recommendation.
What is the half life of Follistatin 344?
Estimated at several hours; precise human pharmacokinetic data are not well established. That is what sets the dosing frequency, and it is why the timing guidance is morning.
How is Follistatin 344 administered?
Subcutaneous: into fat, under the skin. Some research protocols use intramuscular injection at the target muscle for a more localized effect.
How long is a Follistatin 344 cycle?
4-8 weeks on, followed by 8-12 weeks off. Given the lack of long-term human safety data, conservative and infrequent cycling is generally discussed rather than continuous use.
What are the side effects of Follistatin 344?
Reported side effects include unknown long-term safety profile in humans, theoretical risk from broad inhibition of activin/tgf-beta signaling, which regulates reproductive and other tissues, injection site reactions, possible unpredictable effects given non-selective binding across the tgf-beta superfamily. Evidence level for this compound is emerging research.
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Educational use only, not medical advice. This profile is provided for research and educational purposes. Follistatin 344 may be a research compound or a prescription medication; nothing here is intended to diagnose, treat, cure, or prevent any disease. Dosing figures reflect commonly-published research ranges, not a prescription. Consult a qualified healthcare provider before making any health decision. Read the full disclaimer →