IGF-1 LR3 vs PEG-MGF vs Follistatin-344: Muscle-Growth Research Compounds Compared
IGF-1 LR3, PEG-MGF and Follistatin-344 all appear in muscle-growth research, but they work through three different systems. IGF-1 LR3 activates growth signaling, PEG-MGF models a local repair signal from loaded muscle, and Follistatin-344 removes a brake on growth. Knowing which lever each one pulls is the key to choosing between them.
At a glance
| IGF-1 LR3 | PEG-MGF | Follistatin-344 | |
|---|---|---|---|
| What it is | Modified IGF-1 (83 amino acids) | Pegylated mechano growth factor (an IGF-1 splice-variant peptide) | Precursor form of follistatin, a binding glycoprotein |
| How it acts | Activates the IGF-1 receptor | Studied for local repair signaling distinct from systemic IGF-1 | Binds and neutralizes myostatin and activin |
| Key pathways | PI3K/Akt, mTOR, MAPK | Satellite-cell activation, myoblast proliferation | SMAD2/3 (TGF-β family) signaling |
| Lever | Accelerator | Local repair signal | Releases the brake |
IGF-1 LR3: a longer-lasting growth signal
Native IGF-1 is quickly captured by IGF-binding proteins, which limits how much reaches the receptor. IGF-1 LR3 replaces the glutamic acid at position 3 with arginine and adds a 13-amino-acid extension at the start. Together these changes sharply reduce binding-protein capture, so more of the peptide stays active for longer. It is widely used as a cell-culture supplement and to study IGF-1 receptor signaling, protein synthesis and myoblast proliferation. IGF-1 LR3 research profile.
PEG-MGF: modeling the local repair response
The IGF-1 gene can be spliced in several ways. One variant, called mechano growth factor (MGF), is produced in muscle after mechanical load or damage and is studied for its role in activating satellite cells, the muscle’s resident stem cells. The free peptide breaks down within minutes, so the research form is pegylated: attached to polyethylene glycol, which protects it and extends its activity. PEG-MGF research profile.
Follistatin-344: releasing the brake
Myostatin, a member of the TGF-β family, limits how large muscle can grow. Follistatin binds myostatin and the related protein activin and stops them reaching their receptors. Follistatin-344 is the 344-amino-acid precursor that is processed into the shorter forms found in tissue. It is used to study myostatin and activin signaling and SMAD pathway activity. Follistatin-344 research profile.
Choosing for a study design
Growth-factor receptor signaling, protein synthesis or cell-culture support: IGF-1 LR3.
Satellite-cell activation and the response to mechanical load or injury: PEG-MGF.
Myostatin and activin biology: Follistatin-344.
Comparing routes to growth: run an accelerator (IGF-1 LR3) against a brake-release (Follistatin-344) in the same model.
Upstream of all three sits the growth-hormone axis. For compounds that act there, see our guides to growth hormone secretagogues and CJC-1295 and Tesamorelin.
Handling and testing
These are larger, more fragile molecules than most short peptides. Keep sealed vials at -20°C, avoid repeated freeze-thaw cycles, and see our storage guide. Every lot we sell is tested by Bioviridian Labs (ISO/IEC 17025, Texas) for HPLC purity, mass-spectrometry identity, endotoxin and heavy metals. See the COA Library.
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For laboratory research use only. Not for human or veterinary use. This article summarizes published research for educational purposes and does not provide medical advice.