Comparison
Follistatin (FST) vs. Sermorelin
Two peptides side-by-side — identity, evidence base, legal status and known adverse events.
Identity
Category
Growth
Growth
CAS no.
122956-17-2
86168-78-7
Molecular weight
35000 g/mol
3358 g/mol
Half-life
no data
0.2 h
Sequence
Glykoprotein, ~315 Aminosäuren in der zirkulierenden Hauptform (Sequenz isoformabhängig, kein einheitliches kurzes Peptid)YADAIFTNSYRKVLGQLSARKLLQDIMSRMechanism of action
Follistatin (FST)
Follistatin binds with high affinity to activin and to myostatin (GDF-8), as well as related TGF-β ligands such as GDF-11 and some BMPs, preventing their binding to the activin type-II receptors. Myostatin is a negative regulator of skeletal muscle mass; by sequestering myostatin, its growth-inhibiting signalling is removed (de-repression). Because follistatin additionally neutralises activin, it acts on several muscle-inhibiting pathways at once — in animal models this produced greater muscle gain than knocking out myostatin alone. Several isoforms exist (including FST-288 and FST-315) that differ in tissue binding via heparan sulfate. The FST344 variant used in gene therapy was chosen to reduce binding to off-target structures.
Sermorelin
Synthetic analogue of the first 29 amino acids of human growth-hormone-releasing hormone (GHRH). Stimulates pulsatile endogenous growth-hormone secretion from the pituitary via the GHRH receptor. Very short plasma half-life — pharmacodynamic effect lasts several hours nevertheless.
Evidence base
Highest evidence
Human trial
Human RCT
Studies
4
5
of which in humans
1
3
Effects recorded
4
3
Open conflicts
1
1
Documented adverse events
1
3
Legal status
Full entries
Frequently asked questions
- What is the difference between Follistatin (FST) and Sermorelin?
- Follistatin (FST) is classified as "Growth", while Sermorelin is classified as "Growth". Follistatin (FST): Follistatin is an endogenous glycosylated binding protein (~35 kDa, considerably larger than typical peptides) that binds and neutralises members of the TGF-β superfamily, including activin and myostatin (GDF-8). In animal models, raising follistatin de-represses muscle growth. Clinically it has been studied mainly via AAV gene therapy (FS344) in muscular dystrophies. Follistatin is not an approved drug; human efficacy and safety data are limited and stem mostly from early gene-therapy trials and preclinical research. A 'follistatin-344' product is sold on the grey market, the identity and purity of which cannot be verified without analytics. Sermorelin: Synthetic analogue of the first 29 amino acids of human GHRH. Stimulates pulsatile growth-hormone secretion from the pituitary. Formerly FDA-approved as Geref Diagnostic, now withdrawn in many markets — compounding and research use dominate. This page contrasts both neutrally and source-based — with no usage or dosing recommendation.
- Which peptide is better supported by science, Follistatin (FST) or Sermorelin?
- The highest available evidence level is "Human trial" for Follistatin (FST) and "Human RCT" for Sermorelin. A higher evidence level means more robust data, but says nothing about suitability for an individual. The full body of evidence is on each peptide's own page.
- What is the legal status of Follistatin (FST) and Sermorelin in Germany and the United States?
- Germany: Follistatin (FST) — Unapproved, Sermorelin — Unapproved. United States: Follistatin (FST) — Unapproved, Sermorelin — Research only. These are factual summaries with source and review date on the individual pages.