Follistatin
Follistatin (Myostatin/Activin-Binding Protein, FST)
Mechanism of Action
Binds and neutralizes myostatin (GDF-8) and activin A, TGF-β superfamily ligands that normally signal through ActRIIB to restrain skeletal muscle hypertrophy. Follistatin-knockout and follistatin-overexpression animal models show this pathway is a primary regulator of muscle size independent of exercise or nutrition.
Key Benefits
- Increased muscle size and strength in follistatin-overexpression animal models
- Mechanistic case for lean-mass preservation during rapid weight loss (GLP-1/incretin era research)
- Validated drug target — multiple myostatin/activin-pathway inhibitors now in human clinical trials
- No organ-system pathology observed in translational (mouse-to-monkey) muscle studies using engineered delivery
Dosing Protocol
The mechanism is genuinely well-established — this isn't a fringe target, it's the same pathway several pharma-grade drugs are being built around. What's thin is direct human trial data on injectable follistatin itself; most of the rigorous data is animal, gene-therapy-delivered, or about the broader pathway rather than the free peptide.
Ideal Candidates
Research contexts modeling myostatin-pathway biology or lean-mass preservation during aggressive weight loss. No published human RCT establishes a safe/effective dose for the free peptide itself.
Side Effects & Safety
No established human safety data for the free peptide. Follistatin also suppresses FSH — the muscle-disease gene-therapy literature flags a theoretical concern for off-target hypothalamic-pituitary-gonadal axis effects at systemic exposure.
Regulatory Status
Gray AreaNot on the 503A bulks list. Mechanism is well-established preclinically; direct human trial data on the injectable peptide itself is thin. Don't confuse follistatin with the myostatin-pathway drugs (bimagrumab, trevogrumab, garetosmab) now in human clinical development — those are separate molecules targeting the same pathway.
Evidence & Citations
How we source and weigh evidence- Lee SJ, et al. Regulation of muscle mass by follistatin and activins. Mol Endocrinol. 2010;24(10):1998-2008.
- Rodino-Klapac LR, et al. Inhibition of myostatin with emphasis on follistatin as a therapy for muscle disease. Muscle Nerve. 2009;39(3):283-96.
- Stefanakis K, Kokkorakis M, Mantzoros CS. The impact of weight loss on fat-free mass, muscle, bone and hematopoiesis health. Metabolism. 2024;161:156057.
Frequently asked
What is Follistatin?+
Follistatin (Follistatin (Myostatin/Activin-Binding Protein, FST)) is a peptide studied for myostatin inhibition and lean mass preservation. Binds and neutralizes myostatin (GDF-8) and activin A, TGF-β superfamily ligands that normally signal through ActRIIB to restrain skeletal muscle hypertrophy. Follistatin-knockout and follistatin-overexpression animal models show this pathway is a primary regulator of muscle size independent of exercise or nutrition.
What is the dosing protocol for Follistatin?+
Literature commonly references 100 mcg/day SubQ (research-community convention; not clinically validated) (low) to 200–300 mcg/day SubQ (research-community convention; not clinically validated) (maintenance) via SubQ (research use), on a no clinically established human protocol cycle. Educational reference only — a licensed Stackhaus Health provider sets any personalized protocol.
What is the regulatory status of Follistatin?+
Not on the 503A bulks list. Mechanism is well-established preclinically; direct human trial data on the injectable peptide itself is thin. Don't confuse follistatin with the myostatin-pathway drugs (bimagrumab, trevogrumab, garetosmab) now in human clinical development — those are separate molecules targeting the same pathway.
Where can I access Follistatin?+
Research-grade Follistatin is available through Stackhaus Research. For a personalized, provider-reviewed protocol, consult a licensed clinician through Stackhaus Health.