Follistatin

Last Updated: August 2026

Follistatin is an activin-binding glycoprotein researched for myostatin inhibition, muscle growth promotion, fibrosis reduction, and tissue remodeling support. It is one of the more pharmacologically distinct compounds in the tissue-repair category — a glycoprotein rather than a small peptide, with substantially larger molecular weight and structural complexity. Several follistatin variants exist (FS-288, FS-315, FS-344) with different tissue-binding properties. Follistatin is not approved for any medical indication and is sold as a research-use-only compound by third-party laboratories.

What is Follistatin and how does the myostatin-binding mechanism work?

Follistatin is an activin-binding glycoprotein that neutralizes myostatin (also called GDF-8), the TGF-β family member that negatively regulates skeletal muscle mass. By sequestering myostatin and related TGF-β superfamily members (activin A, GDF-11), follistatin removes the brake on muscle growth and supports anabolic muscle remodeling. The biological effect is well-characterized — myostatin knockout produces dramatically enhanced muscle mass in animal models, and natural human follistatin variants are associated with muscle mass variation. Several follistatin variants (FS-288, FS-315, FS-344) have different tissue-binding properties. Of these, follistatin-344 (FS-344) — the 344-residue precursor form that the body processes toward the circulating FS-315 isoform, and the form used in most injectable and AAV gene-therapy research — has its own dedicated profile: see Follistatin-344. That page and this one describe the same protein at different levels of specificity — follistatin-344 is a particular isoform of follistatin, not a separate molecule — so their data should be read together, not merged. Evidence level: Established biology (myostatin pathway); preclinical extensive; limited human clinical research.

What does the research show for Follistatin?

Preclinical studies have demonstrated substantial muscle mass increases through myostatin inhibition across rodent and other animal models. Phase 1/2 clinical research has been conducted in Duchenne muscular dystrophy and inclusion body myositis contexts with limited efficacy signals. Gene therapy approaches to follistatin delivery (AAV-follistatin) are in earlier-stage research for muscular dystrophy indications. Recombinant follistatin protein therapy has not advanced to formal Phase 3 approval. Evidence level: Preclinical extensive; Phase 1/2 in muscular dystrophy contexts; no Phase 3 approval.

How does Follistatin compare to other tissue-repair peptides?

Follistatin is mechanistically distinct from BPC-157 and TB-500 — its primary effect is muscle-specific via myostatin inhibition rather than broad tissue repair, and it is a much larger glycoprotein rather than a small peptide.

What are the documented side effects of Follistatin?

Side effects in available clinical research and community-reported research use are generally mild — injection-site reactions are the most common report. The myostatin inhibition mechanism raises theoretical concerns about effects on muscle composition, cardiac muscle (myostatin is expressed in cardiac tissue), and reproductive function (activin is involved in gonadotropin regulation). Long-term safety at sustained dosing is not characterized at Western RCT standards. Evidence level: Phase 1/2 safety; long-term and cardiac unestablished; theoretical concerns reflect mechanism biology.

What is the regulatory status of Follistatin?

Follistatin is not approved for any medical indication anywhere in the world as of August 2026. Phase 1/2 clinical research has been conducted in muscular dystrophy contexts without advancing to Phase 3 approval. The compound was not specifically included in the April 2026 FDA Category 2 removals. Follistatin is sold strictly as a research-use-only material by third-party laboratories. Regulatory context in are peptides legal regulatory status by country.

Why does Follistatin vendor verification matter?

Follistatin is a glycoprotein with substantially larger molecular weight and structural complexity than small peptides — synthesis, expression (typically recombinant), and quality control are fundamentally different and more variable. Different follistatin variants (FS-288, FS-315, FS-344) have different properties. Independent HPLC, mass spectrometry, and ideally glycosylation analysis are essential — though research-grade analytical standards may not fully match pharmaceutical-grade glycoprotein verification. Guidance in how-to-test-peptides hub (note: peptide-specific guidance does not all directly apply to glycoproteins).

How does Peptigrity verify Follistatin vendors?

Peptigrity collects independent third-party Certificates of Analysis for follistatin from shops' official channels and verifies each for authenticity before publishing. Because shops choose which COAs to publish, results reflect the batches shops have made public rather than every production batch — a selection bias we state openly. A community-funded Testing Grant to purchase and test vials anonymously is in development. Follistatin's glycoprotein nature limits the discriminating power of standard peptide tests, so HPLC, mass spectrometry, and ideally glycosylation analysis matter more here than for small peptides. Tests in the database come from independent labs such as Janoshik Analytical, Freedom Diagnostics, and Chromate. Methodology in how we calculate trust scores.

Frequently Asked Questions

What does Follistatin do?

Follistatin neutralizes myostatin to remove the natural brake on muscle growth, producing substantial muscle mass increases in preclinical models. Human clinical evidence is more limited, with Phase 1/2 research in muscular dystrophy contexts not advancing to Phase 3 approval.

Is Follistatin legal to purchase?

Follistatin is legal to purchase as a research chemical for laboratory use in most jurisdictions, but it is not approved for human consumption. Country breakdown in peptide legal status guide.

Will Follistatin be FDA-approved?

No active formal clinical development program has advanced Follistatin to FDA approval as of August 2026. Phase 1/2 work in muscular dystrophy has not produced sufficient efficacy signal to advance to Phase 3.

Does Follistatin affect the heart?

Myostatin is expressed in cardiac tissue as well as skeletal muscle, so the myostatin inhibition mechanism raises theoretical concerns about cardiac effects. Clinical substantiation of these concerns is limited but the mechanism biology supports caution. Anyone considering Follistatin use should consult a licensed physician about the underlying pathway biology.

How can I verify a Follistatin vendor is selling real product?

Independent third-party HPLC certificate of analysis from a lab the vendor does not own or pay, with mass spectrometry identity confirmation. Note that for a glycoprotein, standard peptide testing has less discriminating power; pharmaceutical-grade glycosylation analysis is not standard in research-grade markets. Verify which follistatin variant (FS-288, FS-315, FS-344) is being sold. COA interpretation in red flags in peptide certificates of analysis.

Does Peptigrity recommend a Follistatin dose?

No. Follistatin is not approved for human consumption and Peptigrity is an independent review platform, not a medical authority. Research-use dosing varies widely. Anyone considering use should consult a licensed physician.

Does Follistatin show up on a drug test?

Yes. Follistatin is named on the WADA Prohibited List under S4.3 (Agents Preventing Activin Receptor IIB Activation) — the subsection that prohibits "myostatin-binding proteins (e.g. follistatin)" — and it is banned at all times, in and out of competition.1 source For drug-testing context, see do peptides show up on drug tests.

This section is for educational and informational purposes only and does not constitute medical advice. Follistatin is not approved by the FDA or any major Western regulator for human use, and it is prohibited by WADA as a myostatin function modifier. Always consult a qualified healthcare provider before using any peptide or research compound. Peptigrity is an independent review platform and does not sell, endorse, or recommend specific products or vendors.