Both come from the IGF-1 gene, but one is a long-acting systemic growth factor and the other a short-lived local repair signal — and they do different jobs in muscle.
Research reference only. Not medical advice, prescribing guidance, or a product recommendation.
| Dimension | IGF-1 LR3 | MGF |
|---|---|---|
| Origin | Modified long-acting IGF-1 analog | Splice variant of IGF-1 (IGF-1Ec) |
| Action radius | Systemic | Local (site of mechanical stress) |
| Duration | Prolonged (hours–days) | Transient (rapid, post-damage) |
| Primary effect | Hypertrophy — protein synthesis in existing fibers | Satellite-cell proliferation (new myonuclei) |
| Key modification | Arg-3 substitution + N-terminal extension (↓ IGFBP binding) | Exon-5 insert → distinct C-terminal E-peptide |
| Potency note | ~2–3× native IGF-1 | Pulse signal, not sustained |
| Status | Research / cell-culture; WADA-banned | Research; WADA-banned |
MGF is the splice variant the body upregulates immediately after mechanical overload or muscle damage; its role is to activate satellite cells, expanding the pool of cells that can fuse and donate nuclei (McKoy, Ashley, Yang et al., 1999; Goldspink group, UCL). IGF-1 LR3 is engineered for a long half-life — an arginine-3 substitution and N-terminal extension reduce IGF-binding-protein binding — and acts systemically to sustain protein synthesis over hours to days.
The sequence in the literature is therefore: MGF initiates the repair phase, IGF-1 LR3 sustains it. A nuance worth stating is that running both simultaneously may be counterproductive, since IGF-1 can drive premature differentiation before MGF has expanded the satellite-cell pool.
These are complementary, not interchangeable: MGF is the local, transient initiator of repair; IGF-1 LR3 is the systemic, long-acting driver of hypertrophy. Both are research compounds (IGF-1 LR3 is also a cell-culture standard), neither is FDA-approved, and both are prohibited in sport. This page is a research and educational reference.
IGF-1 LR3 is a modified, long-acting, systemic IGF-1 analog studied for hypertrophy via sustained protein synthesis. MGF (mechano growth factor) is a local IGF-1 splice variant upregulated after muscle damage that activates satellite cells. MGF initiates repair; IGF-1 LR3 sustains it.
In the research literature they are typically sequenced rather than combined simultaneously, because IGF-1 may promote premature differentiation before MGF has expanded the satellite-cell pool.
An arginine-3 substitution and a 13-residue N-terminal extension reduce its binding to IGF-binding proteins, leaving more peptide free and active and extending its half-life versus native IGF-1.
No. Both are research compounds — IGF-1 LR3 is also widely used in cell culture — and neither is FDA-approved; both are prohibited in sport. This page is a research and educational reference.