Comparison

Follistatin (FST) vs. IGF-1 LR3

Two peptides side-by-side — identity, evidence base, legal status and known adverse events.

Identity

Mechanism 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.

IGF-1 LR3

IGF-1 LR3 is a recombinantly produced variant of human IGF-1. Two changes define its properties: (1) at position 3, glutamic acid is replaced by arginine; (2) a 13-amino-acid sequence is added at the N-terminus ('Long'). Both modifications drastically reduce affinity for the six IGF-binding proteins (IGFBP-1 to -6) that normally bind native IGF-1 in the blood and regulate its availability at the receptor. As a result, a larger fraction of the molecule is freely available to bind the type-1 IGF receptor (IGF-1R) — the same receptor as native IGF-1. In preclinical models and cell culture, LR3 IGF-1 therefore acts as a more potent agonist than unmodified IGF-1. The downstream signalling pathway (PI3K/Akt and MAPK) is identical to that of IGF-1; the modification changes bioavailability, not the receptor target.

Evidence base

Highest evidence

Human trial

Animal model

Studies

of which in humans

Effects recorded

Open conflicts

Documented adverse events

Legal status

Country	Follistatin (FST)	IGF-1 LR3
Germany	Unapproved	Unapproved
United States	Unapproved	Unapproved

Full entries

Frequently asked questions

What is the difference between Follistatin (FST) and IGF-1 LR3?: Follistatin (FST) is classified as "Growth", while IGF-1 LR3 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. IGF-1 LR3: Synthetic analogue of insulin-like growth factor 1 (IGF-1) carrying an arginine substitution at position 3 and a 13-amino-acid N-terminal extension. These modifications lower binding to IGF-binding proteins and extend its duration of action relative to native IGF-1. LR3 IGF-1 is primarily an established cell-culture reagent (serum-free media, bioprocessing); it is NOT an approved human medicine. Use in the bodybuilding grey market is described; as an IGF-1 analogue, LR3 IGF-1 falls under the WADA anti-doping prohibition. This page contrasts both neutrally and source-based — with no usage or dosing recommendation.
Which peptide is better supported by science, Follistatin (FST) or IGF-1 LR3?: The highest available evidence level is "Human trial" for Follistatin (FST) and "Animal model" for IGF-1 LR3. 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 IGF-1 LR3 in Germany and the United States?: Germany: Follistatin (FST) — Unapproved, IGF-1 LR3 — Unapproved. United States: Follistatin (FST) — Unapproved, IGF-1 LR3 — Unapproved. These are factual summaries with source and review date on the individual pages.

Country

Follistatin (FST)

IGF-1 LR3

Germany

Unapproved

United States

Unapproved

Frequently asked questions

What is the difference between Follistatin (FST) and IGF-1 LR3?

Follistatin (FST) is classified as "Growth", while IGF-1 LR3 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. IGF-1 LR3: Synthetic analogue of insulin-like growth factor 1 (IGF-1) carrying an arginine substitution at position 3 and a 13-amino-acid N-terminal extension. These modifications lower binding to IGF-binding proteins and extend its duration of action relative to native IGF-1. LR3 IGF-1 is primarily an established cell-culture reagent (serum-free media, bioprocessing); it is NOT an approved human medicine. Use in the bodybuilding grey market is described; as an IGF-1 analogue, LR3 IGF-1 falls under the WADA anti-doping prohibition. This page contrasts both neutrally and source-based — with no usage or dosing recommendation.

Which peptide is better supported by science, Follistatin (FST) or IGF-1 LR3?

The highest available evidence level is "Human trial" for Follistatin (FST) and "Animal model" for IGF-1 LR3. 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 IGF-1 LR3 in Germany and the United States?

Germany: Follistatin (FST) — Unapproved, IGF-1 LR3 — Unapproved. United States: Follistatin (FST) — Unapproved, IGF-1 LR3 — Unapproved. These are factual summaries with source and review date on the individual pages.