IGF-1 LR3
A supercharged version of IGF-1 (a key growth factor your liver produces in response to growth hormone). Modified to stay active much longer and avoid being deactivated by binding proteins. One of the most powerful muscle-building peptides available — it can actually create new muscle cells, not just make existing ones bigger. However, this potency comes with serious risks including dangerously low blood sugar and potential tumour promotion.
Dosage
20-80 mcg subcutaneous or intramuscular once daily
Dosages shown are for research reference only. Always consult a qualified healthcare provider.
Administration
Get Research-Grade IGF-1 LR3
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Effects
Muscle Growth
Extremely potent anabolic — can promote muscle cell hyperplasia (new cells), not just hypertrophy.
Fat Loss
Promotes fat breakdown while redirecting nutrients toward muscle tissue.
Recovery
Accelerates tissue repair and supports connective tissue healing.
Mechanism of Action
IGF-1 LR3 is an 83-amino-acid analogue of native IGF-1 (70 amino acids) featuring two critical modifications: an arginine substitution at position 3 (replacing glutamic acid) and a 13-amino-acid N-terminal extension peptide. These modifications dramatically reduce binding affinity for the six IGF binding proteins (IGFBP-1 through IGFBP-6) that normally sequester over 98% of circulating IGF-1, effectively increasing the free, bioactive fraction by orders of magnitude.
Free IGF-1 LR3 binds to the IGF-1 receptor (IGF-1R), a receptor tyrosine kinase structurally similar to the insulin receptor. Receptor activation triggers autophosphorylation and recruitment of insulin receptor substrate (IRS) proteins, activating two major downstream cascades: the PI3K/Akt/mTOR pathway (driving protein synthesis, cell survival, and glucose uptake) and the Ras/MAPK/ERK pathway (promoting cell proliferation and differentiation). The potent activation of mTORC1 through Akt directly stimulates ribosomal protein S6 kinase and inhibits 4E-BP1, dramatically increasing the rate of translation and muscle protein synthesis.
What makes IGF-1 LR3 particularly potent for muscle growth compared to GH or native IGF-1 is its ability to promote muscle cell hyperplasia — the creation of entirely new muscle cells from satellite cell differentiation — rather than solely hypertrophy (enlarging existing cells). IGF-1R signaling in satellite cells activates MyoD and myogenin expression, driving proliferation and fusion into existing myofibers. The 20-30 hour half-life of LR3 (compared to 12-15 minutes for native IGF-1) means sustained receptor activation, continuous anabolic signaling, and significantly greater biological potency per dose. However, this same potency carries risks: strong insulin-like hypoglycemic effects, potential promotion of tumor growth through anti-apoptotic signaling, and possible organ hypertrophy with chronic use.
Regulatory Status
Not FDA approved. Research compound. Mecasermin (native IGF-1) is FDA approved for IGF-1 deficiency. LR3 variant is not approved for any medical use.
Risks & Safety
Common
low blood sugar, joint pain, headache, jaw and hand growth with prolonged use.
Serious
may promote existing tumour growth, organ enlargement (gut, heart) with long-term use, severe low blood sugar requiring emergency treatment.
Rare
nerve damage, enlarged facial features.
Compare IGF-1 LR3 With
Research Papers
9Published: January 17, 2026
AI Summary
Volumetric muscle loss (VML) resulting from severe extremity injuries in combat remains a significant clinical challenge, particularly in austere environments. Current research emphasizes the development and evaluation of definitive treatments, largely neglecting acute stabilization strategies. To address this unmet need, this study investigated the efficacy of delivering insulin-like growth fa...
Published: November 24, 2025
AI Summary
Peripheral nerve injuries lead to significant functional deficits, with no treatment achieving complete recovery. Autologous nerve grafting remains the gold standard, but it is limited by donor site morbidity. Artificial nerve conduits have been developed but have not matched the outcomes of autologous grafts.
Published: December 31, 2024
AI Summary
Insulin-like growth factor-1 (IGF-1) and insulin are important fetal anabolic hormones. Complications of pregnancy, such as placental insufficiency, can lead to fetal growth restriction (FGR) with low-circulating IGF-1 and insulin concentrations and attenuated glucose-stimulated insulin secretion (GSIS), which likely contribute to neonatal glucose dysregulation. We previously demonstrated that ...
Published: January 28, 2025
AI Summary
Insulin-like growth factor-1 (IGF-1) promotes neurogenesis, cell survival, and glial function, making it a promising candidate therapy in Alzheimer's disease (AD)..
Published: June 30, 2023
AI Summary
Insulin-like growth factor-1 (IGF-1) is a pleiotropic protein hormone and has become an attractive therapeutic target because of its multiple roles in various physiological processes, including growth, development, and metabolism. However, its production is hindered by low heterogenous protein expression levels in various expression systems and hard to meet the needs of clinical and scientific ...
Published: June 27, 2023
AI Summary
Insulin-like growth factor-1 (IGF-1) is a critical fetal growth hormone that has been proposed as a therapy for intrauterine growth restriction. We previously demonstrated that a 1-week IGF-1 LR3 infusion into fetal sheep reduces in vivo and in vitro insulin secretion suggesting an intrinsic islet defect. Our objective herein was to determine whether this intrinsic islet defect was related to c...
Published: November 28, 2022
AI Summary
Cell surface proteins carrying N-glycans play important roles in inter- and intracellular processes including cell adhesion, development, and cellular recognition. Dysregulation of the glycosylation machinery has been implicated in various diseases, and investigation of global differential cell surface proteome effects due to the loss of N-glycosylation will provide comprehensive insights into ...
Published: August 24, 2022
AI Summary
IGF-1 is a critical fetal growth-promoting hormone. Experimental infusion of an IGF-1 analog, human recombinant LR3 IGF-1, into late gestation fetal sheep increased fetal organ growth and skeletal muscle myoblast proliferation. However, LR3 IGF-1 has a low affinity for IGF binding proteins (IGFBP), thus reducing physiologic regulation of IGF-1 bioavailability.
Published: May 31, 2021
AI Summary
Insulin and insulin-like growth factor-1 (IGF-1) are fetal hormones critical to establishing normal fetal growth. Experimentally elevated IGF-1 concentrations during late gestation increase fetal weight but lower fetal plasma insulin concentrations. We therefore hypothesized that infusion of an IGF-1 analog for 1 wk into late gestation fetal sheep would attenuate fetal glucose-stimulated insuli...
Frequently Asked Questions
What is IGF-1 LR3?
A supercharged version of IGF-1 (a key growth factor your liver produces in response to growth hormone). Modified to stay active much longer and avoid being deactivated by binding proteins. One of the most powerful muscle-building peptides available — it can actually create new muscle cells, not just make existing ones bigger. However, this potency comes with serious risks including dangerously low blood sugar and potential tumour promotion.
What is IGF-1 LR3 used for?
A supercharged version of IGF-1 (a key growth factor your liver produces in response to growth hormone). Modified to stay active much longer and avoid being deactivated by binding proteins. One of the most powerful muscle-building peptides available — it can actually create new muscle cells, not just make existing ones bigger. However, this potency comes with serious risks including dangerously low blood sugar and potential tumour promotion.
What is the dosage for IGF-1 LR3?
Standard: 20-80 mcg subcutaneous or intramuscular once daily. Often cycled 4-6 weeks on, 4 weeks off. Some protocols use site-specific intramuscular injection into target muscles for localized effects.
What are the side effects of IGF-1 LR3?
Common: low blood sugar, joint pain, headache, jaw and hand growth with prolonged use. Serious: may promote existing tumour growth, organ enlargement (gut, heart) with long-term use, severe low blood sugar requiring emergency treatment. Rare: nerve damage, enlarged facial features.
How does IGF-1 LR3 work?
IGF-1 LR3 is an 83-amino-acid analogue of native IGF-1 (70 amino acids) featuring two critical modifications: an arginine substitution at position 3 (replacing glutamic acid) and a 13-amino-acid N-terminal extension peptide. These modifications dramatically reduce binding affinity for the six IGF binding proteins (IGFBP-1 through IGFBP-6) that normally sequester over 98% of circulating IGF-1, effectively increasing the free, bioactive fraction by orders of magnitude. Free IGF-1 LR3 binds to the IGF-1 receptor (IGF-1R), a receptor tyrosine kinase structurally similar to the insulin receptor. Receptor activation triggers autophosphorylation and recruitment of insulin receptor substrate (IRS) proteins, activating two major downstream cascades: the PI3K/Akt/mTOR pathway (driving protein synthesis, cell survival, and glucose uptake) and the Ras/MAPK/ERK pathway (promoting cell proliferation and differentiation). The potent activation of mTORC1 through Akt directly stimulates ribosomal protein S6 kinase and inhibits 4E-BP1, dramatically increasing the rate of translation and muscle protein synthesis. What makes IGF-1 LR3 particularly potent for muscle growth compared to GH or native IGF-1 is its ability to promote muscle cell hyperplasia — the creation of entirely new muscle cells from satellite cell differentiation — rather than solely hypertrophy (enlarging existing cells). IGF-1R signaling in satellite cells activates MyoD and myogenin expression, driving proliferation and fusion into existing myofibers. The 20-30 hour half-life of LR3 (compared to 12-15 minutes for native IGF-1) means sustained receptor activation, continuous anabolic signaling, and significantly greater biological potency per dose. However, this same potency carries risks: strong insulin-like hypoglycemic effects, potential promotion of tumor growth through anti-apoptotic signaling, and possible organ hypertrophy with chronic use.
How is IGF-1 LR3 administered?
IGF-1 LR3 is administered via subcutaneous or intramuscular injection.
What is the half-life of IGF-1 LR3?
The half-life of IGF-1 LR3 is 20-30 hours (compared to 12-15 minutes for native IGF-1).
Is IGF-1 LR3 legal?
Not FDA approved. Research compound. Mecasermin (native IGF-1) is FDA approved for IGF-1 deficiency. LR3 variant is not approved for any medical use.
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