IGF-1 LR3
Insulin-like Growth Factor 1 LR3
IGF-1 LR3 is a synthetic, elongated analog of Insulin-like Growth Factor 1 (IGF-1) with an arginine substitution at position 3 and a 13-amino acid N-terminal extension, giving it a half-life of approximately 20-30 hours compared to native IGF-1's 12-15 minutes. It is primarily used in research contexts and illicitly by bodybuilders and athletes to promote skeletal muscle hypertrophy, enhance recovery, and reduce body fat through potent anabolic and anti-catabolic signaling. Its extended half-life and reduced binding affinity for IGF-binding proteins (IGFBPs) make it significantly more bioactive in peripheral tissues than endogenous IGF-1.
Mechanism of Action
IGF-1 LR3 binds to the IGF-1 receptor (IGF-1R), a tyrosine kinase receptor, activating downstream PI3K/Akt/mTOR and MAPK/ERK signaling cascades that drive protein synthesis, satellite cell activation, and myofibrillar growth. Unlike native IGF-1, its structural modifications dramatically reduce affinity for all six IGF-binding proteins, allowing a far greater proportion of circulating peptide to remain free and biologically active. It also exerts insulin-mimetic effects by cross-reacting with insulin receptors at higher concentrations, stimulating GLUT4 translocation and cellular glucose uptake, which can cause hypoglycemia.
Evidence by Health Goal(13 goals)
Dosing Protocols
Post-workout or upon waking on non-training days; administered subcutaneously or intramuscularly into the target muscle group
Cycle: 4-6 weeks on, 4-6 weeks off
Commonly used in the 40-80mcg range. Beginners should start at 20-40mcg to assess tolerance for hypoglycemia. Reconstitute lyophilized powder with bacteriostatic water; store reconstituted peptide at 2-8°C and use within 3-4 weeks. Consume fast-acting carbohydrates post-injection to mitigate hypoglycemic risk. Longer cycles or continuous use risk downregulation of IGF-1R and potential promotion of abnormal tissue growth.
Safety & Side Effects
IGF-1 LR3 carries a meaningful risk profile including acute hypoglycemia, long-term concerns about promotion of occult malignancies due to its potent mitogenic activity, and receptor desensitization with prolonged use; it is not approved for human therapeutic use in any jurisdiction and is classified as a research chemical. Users with any personal or family history of cancer, diabetes, or cardiovascular disease should avoid use entirely, and cycling protocols are strongly advised to minimize receptor downregulation and reduce oncogenic risk.
Possible Side Effects
- !Hypoglycemia (dizziness, sweating, tremor) — most common acute risk, particularly post-injection without carbohydrate intake
- !Hypoglycemia-induced headache and cognitive impairment
- !Transient localized tissue swelling and edema at injection sites
- !Jaw pain or joint pain due to soft tissue and cartilage growth
- !Facial, hand, or foot tissue thickening with prolonged or high-dose use (acromegalic features)
- !Fatigue and lethargy, particularly during initial adaptation phase
- !Potential promotion of pre-existing neoplastic or dysplastic tissue growth due to mitogenic signaling
- !Antibody formation against the peptide with extended use, reducing efficacy
Interactions
- -Insulin and insulin secretagogues: additive hypoglycemic effect — concurrent use significantly increases risk of severe hypoglycemia
- -Growth hormone (GH): synergistic anabolic effect, but also amplifies hypoglycemia risk and accelerates soft tissue hypertrophy side effects
- -Anabolic steroids (testosterone, nandrolone): may potentiate muscle hypertrophy via complementary receptor pathways; combined use increases cardiovascular strain
- -Antidiabetic medications (metformin, SGLT2 inhibitors): unpredictable glucose dysregulation when combined — avoid concurrent use
- -mTOR inhibitors (rapamycin/sirolimus): directly antagonizes IGF-1 LR3 downstream signaling, substantially blunting anabolic effects
Cost & Where to Buy
Research-grade IGF-1 LR3 is typically sold in vials of 1mg (1000mcg); at 50mcg/day for 30 days a cycle uses approximately 1.5mg. Pricing ranges from $25-80 per 1mg vial depending on vendor and purity verification; pharmaceutical-grade or third-party tested products cost significantly more. Bacteriostatic water and insulin syringes add a small additional monthly cost.
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