Follistatin
Also known as: FST · FST-288 · FST-315 · FST-344 (research naming)
Tag note. Follistatin is technically a protein, not a strict peptide (a chain longer than ~100 amino acids). The community treats it as a peptide because it ships through the same research-peptide and clinic channels; the biochemistry classification is protein. Same data, more accurate label.
Phase 2 gene-therapy trials for muscular dystrophy (Mendell 2015); preclinical myostatin-inhibition data; in vitro mitogenic activity on cancer cell lines; WADA prohibited; no regulatory approvals as a peptide product.
Rating per Panya's data-first method, not regulator endorsement. The mechanism, dose, and risk sections below carry the underlying data.
Follistatin is an endogenous 288-residue glycoprotein that binds and neutralises members of the TGF-beta superfamily including activin, BMPs, and myostatin (GDF-8). Inhibiting myostatin removes a primary brake on muscle growth, which is the basis for the bodybuilder-community use and the Phase 2 muscular dystrophy gene-therapy research.
Last reviewed · Panya.health editorial
Panya scores vendors against an 11-signal rubric. Vendors at or above 70 out of 100 are routable; below 70 are documented but get no Panya affiliate link. For prescription peptides like Mounjaro and Wegovy, Panya routes today through licensed clinicians. For research peptides like Follistatin, vendor scorecards land in a follow-up sprint after legal review and payment processor selection. Until then, the page surfaces commonly-mentioned vendor names so adults can do their own diligence. We do not yet earn commission on any Follistatin vendor.
Not medical advice. Follistatin is not approved for human medical use in most jurisdictions. The data below is what users do; it is not what regulators have validated. You decide your risk profile.
What it does, and how
Follistatin was isolated in 1987 from porcine ovarian fluid as a protein that suppressed pituitary FSH secretion, hence the name. The protein has two main natural isoforms (FST-288 and FST-315) generated by alternative splicing; both bind activin with high affinity and neutralise its signalling. The myostatin-binding activity emerged as a separate research focus in the 1990s and 2000s after McPherron and Lee's work on Belgian Blue cattle and the human child case from Schuelke 2004 demonstrated that myostatin loss-of-function produces dramatic muscle hypertrophy. Follistatin occupies the same activin-binding cleft on myostatin, neutralises it, and removes the negative regulator of muscle satellite-cell proliferation and fibre hypertrophy. The Mendell 2015 Phase 1/2 trial of AAV-delivered FST-344 in Becker muscular dystrophy patients showed measurable functional improvement and is the most-cited human evidence for the muscle-growth mechanism. Follistatin also inhibits BMPs (relevant to bone and reproductive contexts) and inhibin (relevant to FSH feedback), which is the basis for the broader endocrine effects beyond skeletal muscle.
Typical practice
Clinical trials have used AAV-delivered gene therapy (Mendell 2015) at viral-particle doses, not protein-injection doses; that protocol is not transferable to community-injection use. Recombinant follistatin protein injection (the product sold by research-peptide vendors as 'FST-344' though it is typically full-length protein) is not validated by any clinical trial protocol. Community injection protocols documented in user logs run 100 to 300 µg per day subcutaneous, in cycles of 10 to 30 days with breaks, often stacked with anabolic steroid cycles or HGH. Reconstitution: typical 1 mg vial in 1 to 5 mL bacteriostatic water. The half-life of recombinant FST in serum is short (minutes to hours), which is why daily dosing is the community standard despite the absence of human pharmacokinetic data for this delivery route. There is no regulator-validated dose for the muscle-growth use case.
The dosing above is community practice, not a regulator-validated protocol. Trial-validated dosing for Follistatin in humans does not exist for most use cases listed.
Risks and contraindications
Documented adverse events in the Mendell 2015 gene-therapy trial: mild myalgia and a rise in serum creatine kinase consistent with the hypertrophy mechanism, no serious AEs in 6 BMD patients followed 1 to 2 years post-injection. Recombinant-injection community-use AEs are anecdotal: injection-site reactions, joint stiffness, occasional headache. The myostatin-pathway interaction with cancer biology is an open clinical question: in vitro, follistatin and myostatin-pathway antagonists have been reported to affect proliferation in several cancer cell lines (Adams 2019 review covers the breast, prostate, and colorectal cell-line work); whether exogenous follistatin administration affects clinical cancer biology in adults has no controlled trial data either direction. Activin neutralisation outside the muscle context affects pituitary FSH feedback and reproductive function; women in fertility-relevant contexts have particular reasons to consider this mechanism. No trial data exists in pregnancy or lactation cohorts. WADA prohibits follistatin and follistatin-mimetic agents in competitive sport (S2 category, peptide hormones and growth factors).
Where this stands legally
FDA has not approved follistatin as a drug. AAV-delivered FST-344 gene therapy has been studied under FDA INDs for Becker muscular dystrophy (Mendell). Recombinant follistatin protein is sold as a research chemical 'not for human consumption.' WADA-prohibited.
MHRA has no follistatin product approval. Research-peptide channels supply the community-use demand. WADA-prohibited.
EMA has no follistatin product approval. Research-peptide channels supply community demand; the gene-therapy research has been concentrated in US trials. WADA-prohibited.
TGA Schedule 4 for injectable peptides without product registration. Personal-import restrictions apply; ASADA actively tests for follistatin and other peptide hormones in competitive sport.
Not Thai FDA-registered. Available through research-peptide vendors; some Bangkok body-composition clinics compound follistatin in stack protocols. Physician oversight varies sharply.
HSA classifies injectable peptides without product registration as prescription-controlled. Imports for personal use get seized at the border.
Not Vietnam Drug Administration-registered. Research-peptide channels supply the limited community use; HCMC body-composition clinics occasionally compound stack protocols.
Available through wellness clinics serving the bodybuilder + expat-athlete market. BPOM has not issued specific follistatin guidance.
Where users say they source it
Names below are sourced from community discussion. None are currently scored against the Panya 11-signal rubric. Panya does not earn commission on any of these. You can search them yourself; treat the list as a starting point for your own diligence, not an endorsement.
- International research-peptide suppliers with COA per lot (audit identity by mass-spec; recombinant follistatin is at the upper end of typical research-peptide sizes and quality varies)Pending Panya 11-signal audit
- Body-composition clinics in TH and Bali compounding follistatin in stack protocols (case-by-case physician oversight)Pending Panya 11-signal audit
- AAV-delivered gene-therapy research products (US clinical trial context only; not in commerce)Pending Panya 11-signal audit
Full vendor scorecards for Follistatin land in a follow-up sprint after lawyer review and payment processor selection. We will not route users to any vendor that scores below 70 on the rubric.
Papers worth reading directly
- Mendell JR, Sahenk Z, Malik V et al. (2015) A phase 1/2a follistatin gene therapy trial for Becker muscular dystrophy. Mol Ther →
- McPherron AC, Lawler AM, Lee SJ. (1997) Regulation of skeletal muscle mass in mice by a new TGF-beta superfamily member. Nature →
- Schuelke M, Wagner KR, Stolz LE et al. (2004) Myostatin mutation associated with gross muscle hypertrophy in a child. N Engl J Med →
- Lee SJ, McPherron AC. (2001) Regulation of myostatin activity and muscle growth. Proc Natl Acad Sci USA →
- Nakamura T, Takio K, Eto Y et al. (1990) Activin-binding protein from rat ovary is follistatin. Science →
Adjacent reading
Track Follistatin in your peptide journal.
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