Comparison

Follistatin (FST) vs. Mod GRF (1-29)

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.

Mod GRF (1-29)

Synthetic analogue of the first 29 amino acids of growth-hormone-releasing hormone (GHRH 1-29). Four amino-acid substitutions (D-Ala at position 2, Gln at 8, Ala at 15, Leu at 27) are intended to slow degradation by dipeptidyl peptidase-IV and increase enzymatic stability relative to native GHRH. Like the native hormone and sermorelin, it binds the GHRH receptor on somatotroph cells of the anterior pituitary; mechanistically this is expected to stimulate endogenous growth-hormone release. Unlike the DAC-conjugated CJC-1295 variant, it lacks albumin binding, so its duration of action remains short.

Evidence base

Highest evidence

Human trial

Studies

of which in humans

Effects recorded

Open conflicts

Documented adverse events

Legal status

Country	Follistatin (FST)	Mod GRF (1-29)
Germany	Unapproved	Unapproved
United States	Unapproved	Research only

Full entries

Frequently asked questions

What is the difference between Follistatin (FST) and Mod GRF (1-29)?: Follistatin (FST) is classified as "Growth", while Mod GRF (1-29) 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. Mod GRF (1-29): Tetrasubstituted synthetic analogue of GHRH(1-29), traded on the grey market as "CJC-1295 without DAC". Closely related to sermorelin (GHRH 1-29); a short-acting growth-hormone-releasing-hormone analogue often combined with a GHRP/ghrelin mimetic. Not approved as a medicinal product. Direct human trials of this exact analogue are essentially absent; the factual basis relies on related GHRH(1-29) analogues. This page contrasts both neutrally and source-based — with no usage or dosing recommendation.
Which peptide is better supported by science, Follistatin (FST) or Mod GRF (1-29)?: The highest available evidence level is "Human trial" for Follistatin (FST) and "Human trial" for Mod GRF (1-29). 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 Mod GRF (1-29) in Germany and the United States?: Germany: Follistatin (FST) — Unapproved, Mod GRF (1-29) — Unapproved. United States: Follistatin (FST) — Unapproved, Mod GRF (1-29) — Research only. These are factual summaries with source and review date on the individual pages.

Country

Follistatin (FST)

Mod GRF (1-29)

Germany

Unapproved

United States

Unapproved

Research only

Frequently asked questions

What is the difference between Follistatin (FST) and Mod GRF (1-29)?

Follistatin (FST) is classified as "Growth", while Mod GRF (1-29) 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. Mod GRF (1-29): Tetrasubstituted synthetic analogue of GHRH(1-29), traded on the grey market as "CJC-1295 without DAC". Closely related to sermorelin (GHRH 1-29); a short-acting growth-hormone-releasing-hormone analogue often combined with a GHRP/ghrelin mimetic. Not approved as a medicinal product. Direct human trials of this exact analogue are essentially absent; the factual basis relies on related GHRH(1-29) analogues. This page contrasts both neutrally and source-based — with no usage or dosing recommendation.

Which peptide is better supported by science, Follistatin (FST) or Mod GRF (1-29)?

The highest available evidence level is "Human trial" for Follistatin (FST) and "Human trial" for Mod GRF (1-29). 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 Mod GRF (1-29) in Germany and the United States?

Germany: Follistatin (FST) — Unapproved, Mod GRF (1-29) — Unapproved. United States: Follistatin (FST) — Unapproved, Mod GRF (1-29) — Research only. These are factual summaries with source and review date on the individual pages.