Follistatin (FST-344)
Protein that binds and inhibits members of the TGF-β superfamily, most notably myostatin. Myostatin inhibition increases muscle mass in animals and in rare human genetic conditions (myostatin-deficient individuals). Heavy biohacking / bodybuilding interest. Limited human-trial data for any indication.
Educational only — not medical advice. SmartPeptide does not prescribe, diagnose, or treat. Always consult a licensed healthcare provider before using any peptide, supplement, medication, or protocol.
What the research shows
Robust preclinical evidence that follistatin / myostatin-pathway inhibition increases muscle mass in mice and primates. Limited human-trial data for muscular dystrophy (mixed results). No FDA-approved follistatin product for any indication.
What's still experimental
All human therapeutic use. Dosing, route, immunogenicity, cardiac safety, tendon-strength balance, and long-term effects are unestablished.
Anecdotal / community reports
Bodybuilding-community claims of accelerated muscle growth. Reports are confounded by training, diet, and stacking with other compounds. Quality verification of grey-market product is essentially impossible.
Anecdotal reports are NOT scientific evidence. They reflect personal experience and may not generalize.
FDA approval status
Source: openFDA + DailyMed (NIH/NLM)Doses studied in research
No established dose rangeWhat published trials tested or FDA-approved labels specify. Reporting research facts — not a SmartPeptide recommendation.
This is the honest answer for peptides like BPC-157, IGF-1 LR3, MOTS-c, Epitalon and similar research compounds — robust human dose- ranging studies have not been published. Always work with a licensed clinician familiar with experimental peptides if you are considering any use.
How clinicians typically protocol this
Third-party reference · not our recommendationDosing phases, cycle lengths, and administration timing as listed in a compounding-pharmacy clinician reference guide. Shown so you can see what a real protocol looks like — and bring informed questions to a licensed clinician.
Dose numbers, frequencies, and cycle lengths in this panel are extracted from a clinician-facing reference protocol distributed by a US-based compounding pharmacy in November 2025. SmartPeptide has paraphrased all descriptive text and adds no endorsement. Always consult a licensed clinician.
Follistatin has essentially no controlled human safety data. Long-term risks around unregulated muscle growth are unknown.
Myostatin antagonist studied for muscle preservation in wasting conditions.
Protocol phases
AM
10 days on / 10+ days off (short cycles per this reference).
FDA enforcement & recalls
Live · openFDA Drug Enforcement APIMechanism & targets
ChEMBL · UniProt · Open TargetsMolecule (ChEMBL)
View on ChEMBLProtein targets (UniProt)
- FollistatinP19883gene: FSTHomo sapiens· 344 aaReviewed
Multifunctional regulatory protein whose primary function is to antagonize members of the transforming growth factor beta (TGF-beta) superfamily including activin, myostatin, GDF11 or bone morphogenetic proteins (BMPs) (PubMed:11279126, PubMed:16482217, PubMed:18535106). Mechanistically, binds to these ligands in the extracellular space, blocking their type II receptor-binding site to inhibit downstream signaling (PubMed:16482217). Plays an essential role in muscle fiber formation and growth bot…
Live research
PubMed · ClinicalTrials.gov · Europe PMC · OpenAlexClinical trials (ClinicalTrials.gov)
- A Dose-Escalation Study in Participants With Advanced CancerCOMPLETEDNCT01524224 · PHASE1 · n=29 · 2008-01
- Effect of L-arginine on Microcirculation, Myogenesis and Angiogenesis Associated With Aging, Sarcopenia and DiabetesCOMPLETEDNCT04112875 · NA · n=120 · 2016-04
- Effects of Early Exercise Rehabilitation in Severe BurnsUNKNOWNNCT04372550 · NA · n=90 · 2019-11-25
- Exercise and Weight ControlCOMPLETEDNCT02152501 · NA · n=29 · 2016-04
- Effect of 80-mg Atorvastatin on Myocardial EdemaCOMPLETEDNCT02901379 · PHASE3 · n=40 · 2016-10
Europe PMC — 2,618,369 additional records
Includes EU/UK studies and PubMed Central full-text articles. Often surfaces research weeks before PubMed indexes it.
- Efficacy and safety of filgotinib in patients with active radiographic and nonradiographic axial spondyloarthritis: results from OLINGUITO, a phase 3 trial consisting of 2 randomised, placebo-controlled, double-blind, parallel-group studiesBaraliakos X, Maksymowych WP, Navarro-Compán V, et al. · 2027
- Clinical Utility of Anti-reflux Mucosal Intervention for Refractory Gastroesophageal Reflux Disease in Patients With a Hiatal HerniaSaino M, Inoue H, Ushikubo K, et al. · 2027
- Early Gastric Cancer Detected During 15-year Surveillance After Ménétrier Disease Remission and Successfully Treated With Endoscopic Submucosal Dissection: A Case ReportShamoto T, Yamamoto H, Naito T, et al. · 2027
- Innovative Therapeutic Endoscopy of the Upper Gastrointestinal Tract: Review of the Japan Gastroenterological Endoscopy Society Core SessionsIguchi M, Michida T, Abe Y, et al. · 2027Open access
Research volume (OpenAlex topic graph)
Human clinical evidence
Semantic Scholar · AI TLDRs · influence-rankedHuman-study summaries for “follistatin OR myostatin inhibitor” are available on Semantic Scholar but the shared free-tier API quota is exhausted right now. Try refreshing in a few minutes, or check the PubMed and Europe PMC panels above for the same literature.
Research funding & verification
NIH RePORTER · CrossRef DOI registryNIH-funded research
U.S. National Institutes of Health- 1R01AG052962-01A1$500KTGF-beta family members and their binding proteins in aging skeletal muscleSe-Jin Lee · UNIVERSITY OF CONNECTICUT SCH OF MED/DNT · FY2017
- 2R01HD032067-24$485KTransforming growth factor β family signaling pathways in ovarian and uterine biologyMARTIN M. MATZUK · BAYLOR COLLEGE OF MEDICINE · FY2020
- 5R01HD032067-27$476KTransforming growth factor β family signaling pathways in ovarian and uterine biologyMARTIN M. MATZUK · BAYLOR COLLEGE OF MEDICINE · FY2023
- 5R01HD032067-25$476KTransforming growth factor β family signaling pathways in ovarian and uterine biologyMARTIN M. MATZUK · BAYLOR COLLEGE OF MEDICINE · FY2021
Publication landscape
CrossRef · DOI registry- National Natural Science Foundation of China6,610 works
- National Institutes of Health2,570 works
- National Cancer Institute1,039 works
- National Research Foundation of Korea891 works
- Japan Society for the Promotion of Science866 works
- Ministry of Education, Culture, Sports, Science and Technology814 works
Funder diversity is a credibility signal. Research concentrated in a single drug company's funding warrants more scrutiny than research funded across NIH, charities, and academic grants.
Preprints — cutting edge
bioRxiv · medRxiv · via Europe PMCPreprints have NOT been peer-reviewed. They are early research shared by authors before formal validation. Treat findings as preliminary.
- PreprintN6-methyladenosine regulates Influenza A virus mRNA stability yet is rarely found on genomic RNAWu H, Tung W, Wungmaiwo R, et al. · 2026-09-03
- PreprintHierarchical cysteine oxidation controls reversible amyloid formation in an ankyrin repeat proteinSethi A, Darroch H, Magon NJ, et al. · 2026-09-03
- PreprintVitamin D counters bone invasion by mammary cancer through inhibition of inflammation and epithelial-to-mesenchymal transitionLi J, Luco A, Camirand A, et al. · 2026-09-03
- PreprintPancreatic cancer cells breach endothelial barriers through protrusion-driven invasion or endothelial retractionFollain G, Ghimire S, Vaitkevičiūtė M, et al. · 2026-09-03
- PreprintSynergistic targeting of EP300/CBP and EYA co-activators collapses the rhabdomyosarcoma core regulatory circuitGustafson AL, Nance S, Gryder B, et al. · 2026-09-03
- PreprintNuclear Cathepsin L Remodels the Replication Machinery to Create a Therapeutic Vulnerability in Ovarian CancerThirusangu P, Jin L, Rao S, et al. · 2026-09-03
Known risks
Theoretical cardiovascular concerns (myostatin pathway affects cardiac muscle), tendon/ligament strain mismatched to muscle growth, fibrosis. Pharmacokinetics and immunogenicity of recombinant follistatin in chronic use are poorly characterized. Source quality is a major concern.
Reported side effects
Injection-site reactions. Long-term tolerability poorly characterized in humans.
FDA adverse event reports (FAERS)
Updated quarterly by FDAWhat requires medical supervision
Not FDA-approved. Should only be considered under specialty care for genetic muscle disease where appropriate.
Questions for your clinician
- Do I have an indication where myostatin inhibition is being studied?
- What FDA-approved muscle-mass interventions should we exhaust first?
- What's the cardiac monitoring plan if we proceed?