IGF-1 LR3
Long R3 Insulin-like Growth Factor 1
A long-acting analogue of IGF-1 studied in animal models for muscle growth and tissue repair.
Overview
IGF-1 LR3 is a modified version of insulin-like growth factor 1 with an arginine substitution and an N-terminal extension that reduce binding to IGF-binding proteins, extending its half-life to roughly a day. It is studied in animal models for muscle protein synthesis and repair. It is not approved and is prohibited in sport.
Mechanism of action
Activates the IGF-1 receptor, driving cellular growth, proliferation, and protein synthesis; reduced binding-protein affinity prolongs activity.
Key studies & citations
- Animal1992
Insulin-like growth factor-I (IGF-I) and especially IGF-I variants are anabolic in dexamethasone-treated rats
LR3 IGF-I and des(1-3) IGF-I, analogues that bind poorly to IGF-binding proteins, were about 2.5-fold more potent than native IGF-I at reversing catabolism in dexamethasone-treated rats.
Biochemical Journal - Animal1997
Long [R3] insulin-like growth factor-I reduces growth, plasma growth hormone, IGF binding protein-3 and endogenous IGF-I concentrations in pigs
A cautionary species difference: four days of LR3 IGF-I infusion in pigs decreased daily gain, food intake, plasma GH, IGFBP-3 and endogenous IGF-I.
Journal of Endocrinology - Animal2001
Localized Igf-1 transgene expression sustains hypertrophy and regeneration in senescent skeletal muscle
Muscle-restricted IGF-1 expression in mice produced persistent hypertrophy and preserved regenerative capacity into old age, the mechanistic basis for IGF-1 muscle research.
Nature Genetics
Frequently asked questions
Is IGF-1 LR3 allowed in sports?
No. IGF-1 and its analogues are on the WADA prohibited list at all times.