IGF-1 LR3 / Mechano-Growth Factor
The Research-Chemical Bodybuilding IGF-1 Variants
Evidence grade 2 of 5, Thin. Read how the Atlas grades evidence.
The written rationale for this grade is still being prepared.
- FDA
- Not FDA-approved; sold as research chemicals
Reference only. Not medical advice.
What can go wrong
IGF-1 LR3 can cause hypoglycemia through insulin-like activity; potent, sustained IGF-1 signaling raises theoretical concerns about organ/tissue overgrowth and tumor promotion. Products are unregulated research chemicals with unverified purity, potency, and sterility. MGF's short half-life reduces systemic exposure but does not make it a validated or safe therapy.
This is something to take to a clinician. The Atlas can tell you what is known about igf-1 lr3 / mechano-growth factor in general. It cannot tell you what is happening in your body, and the difference matters most for exactly the symptoms that bring people to this page.
IGF-1 LR3 (Long Arg3 IGF-1) is a modified insulin-like growth factor-1 with an Arg substitution at position 3 and a 13-amino-acid N-terminal extension that reduces binding-protein capture and greatly extends its active half-life. Mechano-Growth Factor (MGF, or IGF-1Ec) is a locally expressed IGF-1 splice variant produced in muscle after mechanical stress, marketed for satellite-cell activation. Both are sold as research chemicals to bodybuilders seeking direct IGF-1 signaling. Neither is approved for human use.
Bodybuilding's direct IGF-1 play, potent, hypoglycemia-prone, unproven.
What people take it for
These are the reasons people give for taking it. They are not effects it has been shown to have.
Combinations named above are how people use these compounds together, under names the community gave them. The combinations themselves have not been studied. Evidence for one compound is not evidence for a pair.
How it is supposed to work
IGF-1 LR3 activates the IGF-1 receptor to drive anabolic signaling (PI3K/Akt/mTOR), with its modifications making it longer-acting and less neutralized by IGF binding proteins than native IGF-1. MGF's distinct C-terminal E-peptide is proposed to activate muscle satellite cells locally following damage; its short half-life limits systemic exposure.
Direct IGF-1 signaling is the danger, not just the appeal
Unlike GH secretagogues that raise IGF-1 modestly through the pituitary, LR3 supplies a potent, long-acting IGF-1 agonist directly. That is also its hazard: IGF-1 has insulin-like activity (hypoglycemia risk) and is a broad mitogen, so chronic supraphysiologic exposure raises long-standing, unresolved concerns about promoting neoplastic and other tissue growth. There are no controlled human trials supporting the bodybuilding claims.
Replacement is not the same as a cycle
These deliver IGF-1 receptor agonism well above physiological signaling. Native IGF-1 is tightly regulated by binding proteins and pulsatile GH; LR3 deliberately circumvents that regulation, which is the whole point and the core risk.
What people get wrong
Often said'MGF and LR3 build muscle safely.'
ActuallyMuscle-growth claims rest on preclinical and mechanistic reasoning, not human trials; potent IGF-1 signaling carries hypoglycemia and mitogenic concerns and is unregulated.
Who profits, and who pushes back
Nobody is named here yet, because we have not done that work on this entry. Read that as unfinished. Somebody almost certainly sells this, and somebody almost certainly disputes it. Assume both until we have checked.
Set against the alternatives
LR3 = long-acting, systemic, potent IGF-1 agonist (bigger anabolic and hypoglycemia signal). MGF = short-acting, locally-oriented splice variant emphasizing satellite-cell activation with less systemic exposure. Both are research chemicals, not medicines.
What we do not know
- Do any bodybuilding benefits of LR3/MGF hold up in controlled human study?
- What is the real neoplastic risk of chronic supraphysiologic IGF-1 receptor agonism?
The market for this
What follows describes how this is bought and sold. It is not a buying guide and it is not an endorsement of any seller.
Sold as research chemicals labeled 'not for human consumption'; among the least-regulated corners of the peptide market. Third-party testing of such products frequently finds sub-standard purity.
At a glance
- IGF-1 LR3
- Arg3 substitution + 13-aa N-terminal extension
- LR3 effect
- Reduced binding-protein capture, longer action
- MGF
- IGF-1Ec splice variant, local muscle signaling
- Approval
- None; research-chemical status
What this entry does not yet cover
What follows is unfinished work on our side, not a finding about IGF-1 LR3 / Mechano-Growth Factor. A short entry is not a safe entry.
- Timeline. We have not built the dated record of research and regulatory events.
- Cost and market. We have not documented what it sells for or who sells it.
- Supply chain. We have not mapped where it is made.
- Who uses it. We have not documented the user groups.
- What could change. No forward-looking summary yet.
- Children and teenagers. We have not checked what is known about younger people.
- Where we land. We have not taken a position on this yet.
Sources
No sources recorded for this entry yet. Nothing on this page can be checked against a citation until that changes, so treat it as a summary awaiting its evidence.