Follistatin (FST) is a naturally occurring glycoprotein that binds and inhibits myostatin and related TGF-beta family factors. Because myostatin limits muscle growth, follistatin is studied for its potential to influence skeletal muscle mass. The FST-344 isoform is commonly referenced.

What does research suggest about Follistatin?

Animal studies and experimental gene-therapy research show that increasing follistatin activity or inhibiting myostatin can increase muscle size. However, human evidence for follistatin used as a research-market peptide is essentially absent, so those effects remain unvalidated in that context.

Is Follistatin approved by the FDA or other regulators?

No. Follistatin is not an approved medicine anywhere for general use. It holds a research or experimental status, and the human work that exists is largely confined to gene-therapy and clinical research settings rather than approved products.

Its safety in humans is not established. Manipulating the myostatin pathway has unknown long-term risks, and research-market material is unverified for identity and purity. There is not enough human data to characterise a reliable safety profile.

What are the side effects of Follistatin?

The long-term side-effect profile is unknown because robust human safety data is lacking. Altering a fundamental growth-regulatory pathway raises theoretical concerns, but specific effects have not been well characterised in humans.

What is the legal status of Follistatin?

Follistatin is not an approved medicine and is generally handled as a research or experimental compound rather than a consumer product. Legal status varies by jurisdiction, and it is not authorised for human therapeutic use in the research-peptide market.

Why is follistatin so often mentioned alongside myostatin?

Myostatin is a signalling protein that acts as a brake on muscle growth. Follistatin is discussed because it can bind and inhibit myostatin and related factors, so the two are frequently paired in muscle-growth conversations. Understanding follistatin really means understanding the myostatin pathway it acts on, and that pathway's long-term role in humans is not fully characterised.

Is the follistatin studied in gene-therapy research the same as a research-market peptide?

No, and this is a common point of confusion. The serious human work on follistatin has largely used gene therapy, where a viral vector delivers the follistatin gene so the body produces the protein itself. That is a fundamentally different approach from an injectable 'follistatin' product sold on the research market, and results from one cannot be assumed to carry over to the other.

Why does follistatin get attention despite the lack of human evidence?

Its popularity is driven mostly by striking muscle-growth results in animal models and by the appeal of the myostatin-inhibition concept, rather than by validated human data. On this site follistatin carries a low evidence rating precisely because that gap between preclinical excitement and confirmed human findings is large.

Where can I buy Follistatin and compare vendors?

Use the vendor comparison on this page. It shows only checked, product-specific links and identifies vendor claims, independent documentation and affiliate relationships separately. Availability and legal status can vary by country.

Muscle / Myostatin

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Also known as: FST · FST-344

Evidence grade D — AnecdotalRisk flag

Short answer

A myostatin-pathway protein discussed for muscle growth. Human evidence is essentially absent for research-market use.

Where can you buy Follistatin?

Crystal Peptides. The table lists only product-specific offers that were checked and for which a real destination exists. Missing prices, quantities, stock and laboratory details are not inferred.

What is known?

Follistatin binds and inhibits myostatin and related factors.

What is not established?

Largely experimental (gene-therapy research); research-market peptide use is unvalidated.

Safety

Manipulating the myostatin pathway has unknown long-term human risks; unverified material.

Regulatory status

Not an approved medicine. Research/experimental status.

Not medical advice. This educational reference is not diagnosis, treatment, prescribing, dosing or emergency guidance. Consult a qualified professional before making health-related decisions.

Regulatory or safety concern: This substance may be unapproved for human use, affect the hormonal system, or be subject to regulator or anti-doping restrictions. Check the cited evidence and rules in your jurisdiction.

Vendor comparison

Buy Follistatin: compare vendors

The table lists only product-specific offers that were checked and for which a real destination exists. Missing prices, quantities, stock and laboratory details are not inferred.

Vendor	Product	Documentation	Shipping	Checked	Action
Crystal Peptides Code PEPTIDES10 −10% · discount code details Sponsored	Follistatin research product	Vendor-supplied data COA stated as available Not independently documented	Europe See the localized country store	Jul 18, 2026	View at vendor

Crystal Peptides

Follistatin research product

Code PEPTIDES10 −10% · discount code details

What is it?

Follistatin binds and inhibits myostatin and related factors.

Research and evidence

Follistatin (also written FST, with the FST-344 isoform frequently referenced) is a naturally occurring glycoprotein best known for its role in the myostatin signalling pathway. Myostatin is a member of the TGF-beta superfamily that acts as a brake on skeletal muscle growth; follistatin binds and inhibits myostatin along with several related growth factors, and by neutralising that brake it is theorised to permit increased muscle mass. This mechanism is why follistatin appears so often in discussions of muscle growth, body composition, and "myostatin inhibition." On peptides.cx it is catalogued in the Muscle / Myostatin category as an educational reference entry, not as a product recommendation or a guide to use.

It is important to be honest about where the evidence actually stands. The strongest follistatin data comes from animal models, where boosting follistatin activity or suppressing myostatin produces marked increases in muscle size, and from experimental gene-therapy research in which a follistatin gene is delivered to tissue. Human evidence for follistatin as an injectable research-market peptide is essentially absent: the controlled human work that exists sits in the gene-therapy and clinical-research world, not in the loose "research peptide" market, and those are very different things. That gap matters. A vial sold as "follistatin" is unverified material of unknown identity, purity, and biological activity, and none of the aspirational muscle-growth claims attached to it have been validated in humans in that context.

Follistatin is not an approved medicine and holds a research or experimental status only. Because it manipulates a core growth-regulatory pathway, its long-term effects in humans are genuinely unknown, and deliberately altering the myostatin axis carries risks that have not been characterised. This page summarises what follistatin is, why researchers study it, and the current evidence and safety picture so readers can understand the science accurately. It is educational reference content and does not provide medical advice, dosing, protocols, or sourcing guidance.

Evidence grade: D

Largely experimental (gene-therapy research); research-market peptide use is unvalidated. Muscle-growth effects in models.

Human evidence

Largely experimental (gene-therapy research); research-market peptide use is unvalidated.

Animal and preclinical evidence

Muscle-growth effects in models.

Proposed mechanisms

Myostatin inhibition affecting muscle growth

Safety concerns and known side effects

Manipulating the myostatin pathway has unknown long-term human risks; unverified material.

Unknown long-term profile

Regulatory status

Not an approved medicine. Research/experimental status.

Follistatin research timeline

Late 1980s
Follistatin is first isolated from ovarian follicular fluid and named for its ability to suppress follicle-stimulating hormone (FSH), initially studied as a reproductive-endocrine protein.
1990s
Research establishes follistatin as a binding protein for activin and, following the discovery of myostatin as a negative regulator of muscle mass, it is identified as an inhibitor of the myostatin pathway.
2000s
Preclinical animal studies report substantial muscle-growth effects when follistatin is over-expressed or delivered, driving interest in the myostatin pathway as a target for muscle-wasting conditions.
Early 2010s
Gene-therapy approaches using viral vectors to deliver the follistatin (FST-344) gene are tested in early-phase human trials for muscular dystrophies and inclusion-body myositis, the main context in which follistatin has been studied in people.
Early 2020s
Follistatin appears on the research-chemical and 'research peptide' market marketed toward muscle growth, despite no approval and essentially no validated human evidence for this form of use.
2020s (ongoing)
Follistatin remains an unapproved, experimental compound; regulated development stays confined to gene-therapy research rather than injectable research-peptide products.

Frequently asked questions about Follistatin

What is Follistatin?: Follistatin (FST) is a naturally occurring glycoprotein that binds and inhibits myostatin and related TGF-beta family factors. Because myostatin limits muscle growth, follistatin is studied for its potential to influence skeletal muscle mass. The FST-344 isoform is commonly referenced.
What does research suggest about Follistatin?: Animal studies and experimental gene-therapy research show that increasing follistatin activity or inhibiting myostatin can increase muscle size. However, human evidence for follistatin used as a research-market peptide is essentially absent, so those effects remain unvalidated in that context.
Is Follistatin approved by the FDA or other regulators?: No. Follistatin is not an approved medicine anywhere for general use. It holds a research or experimental status, and the human work that exists is largely confined to gene-therapy and clinical research settings rather than approved products.
Is Follistatin safe?: Its safety in humans is not established. Manipulating the myostatin pathway has unknown long-term risks, and research-market material is unverified for identity and purity. There is not enough human data to characterise a reliable safety profile.
What are the side effects of Follistatin?: The long-term side-effect profile is unknown because robust human safety data is lacking. Altering a fundamental growth-regulatory pathway raises theoretical concerns, but specific effects have not been well characterised in humans.
What is the legal status of Follistatin?: Follistatin is not an approved medicine and is generally handled as a research or experimental compound rather than a consumer product. Legal status varies by jurisdiction, and it is not authorised for human therapeutic use in the research-peptide market.
Why is follistatin so often mentioned alongside myostatin?: Myostatin is a signalling protein that acts as a brake on muscle growth. Follistatin is discussed because it can bind and inhibit myostatin and related factors, so the two are frequently paired in muscle-growth conversations. Understanding follistatin really means understanding the myostatin pathway it acts on, and that pathway's long-term role in humans is not fully characterised.
Is the follistatin studied in gene-therapy research the same as a research-market peptide?: No, and this is a common point of confusion. The serious human work on follistatin has largely used gene therapy, where a viral vector delivers the follistatin gene so the body produces the protein itself. That is a fundamentally different approach from an injectable 'follistatin' product sold on the research market, and results from one cannot be assumed to carry over to the other.
Why does follistatin get attention despite the lack of human evidence?: Its popularity is driven mostly by striking muscle-growth results in animal models and by the appeal of the myostatin-inhibition concept, rather than by validated human data. On this site follistatin carries a low evidence rating precisely because that gap between preclinical excitement and confirmed human findings is large.
Where can I buy Follistatin and compare vendors?: Use the vendor comparison on this page. It shows only checked, product-specific links and identifies vendor claims, independent documentation and affiliate relationships separately. Availability and legal status can vary by country.

Common discussion areas

MyostatinMuscle growth

Sources

Editorial review and transparency

Written by: peptides.cx Editorial Team
Scientific reviewer: No named medical reviewer is currently assigned
Last editorial review: June 1, 2026
Last vendor check: July 18, 2026
Review method: Source review, claim verification, vendor-data separation and regulatory-context review.
Commercial disclosure and conflicts: Vendor relationships do not determine evidence or safety ratings. No named reviewer conflict is recorded because no named reviewer is assigned.

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