Long-acting IGF-1 analogue with arginine substitution and glutamate extension for reduced binding protein affinity. Higher bioavailability than native IGF-1.
IGF-1 LR3 (Long R3 Insulin-Like Growth Factor-1) is a modified version of IGF-1 with an amino acid change and an extension that gives it a much longer half-life than natural IGF-1. It has been studied for its effects on muscle growth, tissue repair, and metabolic signaling. It is primarily a research tool compound and is not FDA-approved.
Muscle and Tissue Research
IGF-1 and its analogs are potent stimulators of muscle protein synthesis and cell growth. Research in cell culture and animal models has examined IGF-1 LR3 for muscle hypertrophy, tissue repair, and recovery. Its extended half-life makes it more practical for research than native IGF-1.
Growth and Development Research
IGF-1 is central to normal growth and development. LR3 analogs have been used in research to understand IGF-1 signaling pathways, receptor interactions, and downstream effects on various cell types.
Metabolic Research
IGF-1 affects glucose and fat metabolism. Research has examined IGF-1 LR3 for effects on insulin sensitivity and metabolic parameters, though the extended half-life and continuous receptor activation make its metabolic effects different from the pulsatile nature of natural IGF-1 signaling.
Strong stimulator of muscle protein synthesis and cellular growth signaling in preclinical studies.
Extended half-life compared to native IGF-1, making it more practical for research applications.
Effects on body composition seen in animal studies consistent with IGF-1 pathway activation.
No completed human clinical trials for performance or body composition applications.
IGF-1 LR3 is a research compound with no human clinical trial safety data for performance or body composition applications. IGF-1 is a powerful growth signal, and its receptors are found throughout the body — including on cancer cells. Sustained IGF-1 receptor activation raises theoretical concerns about promoting the growth of pre-existing abnormal cells. The relationship between elevated IGF-1 and cancer risk is an active research area. This is not a compound for casual use.
IGF-1 (insulin-like growth factor 1) is produced by the liver in response to growth hormone and acts as the main downstream mediator of GH's growth effects. It binds to the IGF-1 receptor on muscle cells, bone cells, and other tissues, triggering protein synthesis and cell growth. Natural IGF-1 has a very short half-life — it is quickly bound by carrier proteins and cleared. LR3 is a modified version with an amino acid substitution and an extension that reduces its binding to carrier proteins, keeping it free and active in the bloodstream for much longer. This makes it a powerful research tool for studying sustained IGF-1 signaling, but the continuous receptor activation is different from the pulsatile nature of normal IGF-1 physiology.
Not FDA-approved. No human clinical trial safety data for non-medical uses. The most significant theoretical concern is the relationship between sustained IGF-1 receptor activation and cancer cell growth — IGF-1 receptors are found on many cancer cell types and are considered growth-promoting. Hypoglycemia is a real risk because IGF-1 has insulin-like effects on glucose metabolism. Research use of this compound carries substantial unknowns regarding long-term safety.
Preliminary
Most evidence comes from preclinical studies and case reports. Human data is limited and more research is needed.
Published Research Ranges
20–100mcg/day in research literature
Research Context Only: These are ranges reported in published scientific studies for educational reference. They are not dosing recommendations. This is not medical advice. Always consult a qualified healthcare professional.
Sources listed here are from the platform research library. All links open the original publication. No citations are generated by AI.
IGF-1 LR3: A Long-Acting Analogue with Reduced IGFBP Binding
Journal of Endocrinology • 2003
• DOI: 10.1677/joe.0.1760129
The National Osteoporosis Foundation's position statement on peak bone mass development and lifestyle factors: a systematic review and implementation recommendations
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Glycogen synthesis and beyond, a comprehensive review of GSK3 as a key regulator of metabolic pathways and a therapeutic target for treating metabolic diseases
Research Education Only: This profile is for educational purposes only. All information is sourced from published scientific literature. This is not medical advice. Not for human consumption. Consult qualified medical professionals for any health decisions.
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