Comparison
Follistatin (FST) vs. Ipamorelin
Two peptides side-by-side — identity, evidence base, legal status and known adverse events.
Identity
Category
Growth
Growth
CAS no.
122956-17-2
170851-70-4
Molecular weight
35000 g/mol
711.86 g/mol
Half-life
no data
2 h
Sequence
Glykoprotein, ~315 Aminosäuren in der zirkulierenden Hauptform (Sequenz isoformabhängig, kein einheitliches kurzes Peptid)Aib-His-D-2-Nal-D-Phe-Lys-NH2Mechanism 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.
Ipamorelin
Ipamorelin is a selective agonist at the GH secretagogue receptor (GHSR-1a). Compared to GHRP-2 and GHRP-6 its selectivity for the growth-hormone axis is higher; ACTH, cortisol and prolactin are not significantly stimulated in clinical studies. This selectivity was the main reason for its development over older GHRPs.
Evidence base
Highest evidence
Human trial
Human RCT
Studies
4
4
of which in humans
1
3
Effects recorded
4
3
Open conflicts
1
1
Documented adverse events
1
1
Legal status
Full entries
Frequently asked questions
- What is the difference between Follistatin (FST) and Ipamorelin?
- Follistatin (FST) is classified as "Growth", while Ipamorelin 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. Ipamorelin: Synthetic pentapeptide and selective growth-hormone secretagogue. Developed at Novo Nordisk in the 1990s as a pentapeptide GHRP successor; clinical development was discontinued after phase 2 (post-operative ileus). This page contrasts both neutrally and source-based — with no usage or dosing recommendation.
- Which peptide is better supported by science, Follistatin (FST) or Ipamorelin?
- The highest available evidence level is "Human trial" for Follistatin (FST) and "Human RCT" for Ipamorelin. 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 Ipamorelin in Germany and the United States?
- Germany: Follistatin (FST) — Unapproved, Ipamorelin — Unapproved. United States: Follistatin (FST) — Unapproved, Ipamorelin — Unapproved. These are factual summaries with source and review date on the individual pages.