IGF-1 LR3
A modified version of insulin-like growth factor 1 with extended half-life. Mediates most of GH's anabolic effects, directly stimulating muscle cell growth via PI3K/Akt/mTOR signaling with theoretical hyperplasia potential.
Mechanism of Action
Binds the IGF-1 receptor, activating PI3K/Akt and mTOR signaling pathways. Directly stimulates muscle cell proliferation and differentiation. The LR3 variant has a much longer half-life than native IGF-1 due to reduced IGFBP binding. May promote muscle fiber hyperplasia (new fiber creation) in addition to hypertrophy. Also has insulin-like glucose-lowering effects.
Typical Dosing
⚠ Warning Flags
- •Hypoglycemia risk similar to insulin
- •Theoretical cancer risk — IGF-1 promotes cell proliferation
- •Potential organ growth with chronic use
- •Very limited human clinical data for performance use
Effect Profile
Side Effect Profile
Research Studies
Insulin-like growth factor I (IGF-I) stimulates protein synthesis and inhibits protein breakdown in humans
Fryburg DA et al. · 1995
Demonstrated that IGF-1 directly stimulates muscle protein synthesis and inhibits proteolysis in human subjects.
Mechanical signals, IGF-I gene splicing, and muscle adaptation
Goldspink G · 2005
Describes how mechano-sensitive IGF-1 splice variants drive muscle hypertrophy and potentially hyperplasia.
The use of IGF-1 in doping in sport
Guha N et al. · 2014
Reviews IGF-1 pharmacology in the context of athletic performance enhancement and its role in mediating GH anabolic effects.