What is IGF-1 LR3?
IGF-1 LR3 (Long R3 Insulin-like Growth Factor-1) is a modified form of IGF-1 with enhanced potency and extended half-life. The modifications include an arginine substitution at position 3 and a 13-amino acid N-terminal extension, making it approximately 2-3 times more potent than native IGF-1.
These modifications prevent binding to IGF binding proteins (IGFBPs), resulting in greater bioavailability and longer duration of action compared to regular IGF-1.
Structural Modifications
Key Changes from IGF-1
- Position 3: Glutamic acid → Arginine (R3)
- N-terminus: 13 amino acid extension added
- Total length: 83 amino acids (vs 70 for IGF-1)
Result of Modifications
- Reduced IGFBP binding (~1000x less)
- Increased half-life
- Greater bioavailability
- Enhanced potency
Molecular Profile
| Property | IGF-1 LR3 | Native IGF-1 |
|---|---|---|
| Amino Acids | 83 | 70 |
| Molecular Weight | ~9200 Da | ~7649 Da |
| Half-life | 20-30 hours | 10-20 minutes |
| IGFBP Binding | Very low | High |
Mechanism of Action
IGF-1 Receptor Activation
- Binds IGF-1 receptors
- Activates PI3K/Akt pathway
- Stimulates protein synthesis
- Promotes cell proliferation
Effects
Anabolic:
- Enhanced protein synthesis
- Muscle hypertrophy
- Cell proliferation
Metabolic:
- Glucose uptake
- Amino acid transport
- Lipid metabolism
Research Interest
Body Composition Studies
- Muscle growth research
- Fat metabolism
- Performance studies
- Regenerative research
Considerations
Potential Risks:
- Hypoglycemia (insulin-like effects)
- Theoretical cancer concerns
- No approved medical uses
- Limited human safety data
Comparison with Other IGF-1 Forms
| Form | Half-life | Potency | IGFBP Binding |
|---|---|---|---|
| IGF-1 | Minutes | Baseline | High |
| IGF-1 LR3 | Hours | Enhanced | Very low |
| IGF-1 DES | Minutes | Higher | Lower |
Summary
IGF-1 LR3 offers enhanced potency and duration through modifications that prevent binding protein sequestration, making it a subject of research interest despite safety unknowns.
Key Points:
- Classification: Modified IGF-1
- Modifications: R3 substitution + N-terminal extension
- Effect: ~2-3x potency of native IGF-1
- Status: Research compound, not approved