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Growth Factor

IGF-1 LR3 Guide & Tableau de Dose

A long-arginine IGF-1 analog studied for anabolic signaling.

Demi-vie~20-30 h
Voiesubcutaneous
IGF-1 LR3 — Tableau de dose
Chaque ligne citée
ObjectifDoseFréquenceDuréePreuveSource
Fetal cardiac and organ growth (fetal sheep model) 0 mcg continuous intravenous infusion 1 week Preclinical PMID 33427051 PMID 33938236
Fetal cardiac growth and coronary vascular development (fetal sheep model) 0 mcg continuous infusion 127 to 134 d gestation (approximately 1 week) Preclinical PMID 32573852
Amyloid plaque remodeling in Alzheimer's disease mouse model (5XFAD mice) 0 mcg per trial 7 months Preclinical PMID 39610283
À des fins de recherche et d'éducation uniquement. Pas un avis médical.

What is IGF-1 LR3?

IGF-1 LR3 — short for Insulin-like Growth Factor-1 Long R3 — is a modified version of a natural hormone your body already makes. The "Long R3" part refers to two structural tweaks: a longer protein tail at one end and a single amino acid swap (arginine instead of glutamate at position 3). Those changes matter a lot in the lab. Natural IGF-1 gets grabbed quickly by binding proteins in the bloodstream, which limits how long it stays active. IGF-1 LR3 has a much lower affinity for those binding proteins, so it stays free and active far longer — making it a useful research tool for studying IGF-1 signaling without needing constant re-dosing.[1] Researchers have also found ways to produce it at scale using yeast-based expression systems, reaching production levels around 1 g/L in bioreactor fermentation, which helps meet the demand for scientific studies.[2]

Important note: IGF-1 LR3 is a research compound, not an approved drug or supplement. Everything on this page is strictly for educational and scientific reference.

How IGF-1 LR3 Works

Think of the IGF-1 receptor on a cell like a door that, when opened, tells the cell to grow, divide, and take up nutrients. Normal IGF-1 is the key — but it often gets intercepted by binding proteins before it even reaches the door. IGF-1 LR3 is like a key coated in Teflon: the binding proteins can't grip it well, so it reaches the receptor more reliably and stays active longer.[1]

Once it docks with the IGF-1 receptor, it triggers a cascade of signals inside the cell — promoting cell growth, protein synthesis, and glucose uptake. In research models, this has been observed across many tissue types, from heart muscle and adrenal glands to nerve cells and pancreatic islets.[5][6]

What the Research Shows

Fetal organ and cardiac growth

Several studies used fetal sheep as a model because fetal development is a period of intense IGF-1-driven growth. A one-week continuous infusion of IGF-1 LR3 into normally growing late-gestation fetal sheep increased the weight of the heart, adrenal gland, and spleen — but did not increase overall body weight, and the growth did not seem to work by pulling more nutrients across the placenta.[6] Interestingly, circulating insulin levels dropped during treatment, which is a finding researchers are still working to fully understand.[6]

Coronary vascular development

When fetal sheep received IGF-1 LR3 from approximately 127 to 134 days of gestation, heart mass increased — and crucially, the coronary blood vessels grew proportionally to match the bigger heart. Coronary conductance (how easily blood flows through those vessels) was preserved per gram of heart tissue, and the vessels responded normally to oxygen changes.[5] This suggests IGF-1 LR3-driven cardiac growth comes with appropriate vascular support, which is an important safety consideration in developmental research.

Growth restriction models

When researchers tested IGF-1 LR3 in growth-restricted fetal sheep — animals whose placentas couldn't deliver enough nutrients — the peptide did not rescue fetal growth. Body weight, insulin, and glucose levels were unchanged compared to untreated controls. One notable finding: circulating amino acids, including branched-chain amino acids important for muscle and insulin signaling, fell during treatment. The researchers speculate that without adequate nutrient supply, IGF-1 LR3 alone cannot drive meaningful growth.[1]

Insulin secretion effects

A short 90-minute infusion of IGF-1 LR3 into fetal sheep suppressed insulin secretion by about 66% during a glucose challenge. However, when the pancreatic islet cells were isolated right after and tested in a dish, they secreted insulin normally — suggesting the suppression happens through a systemic signal, not an intrinsic defect in the beta cells themselves.[3]

Nerve regeneration

In a rat sciatic nerve injury model, IGF-1 LR3 was incorporated into a novel plant-derived nerve conduit that released the peptide in a controlled way. Animals treated with the IGF-1 LR3-releasing conduit showed significantly improved axonal (nerve fiber) regeneration, with outcomes comparable to the gold-standard autologous nerve graft — and no signs of systemic toxicity.[4] This points to potential applications in peripheral nerve repair research.

What IGF-1 LR3 Is Being Studied For

  • Fetal and neonatal growth signaling[1][6]
  • Cardiac growth and coronary vascular development[5]
  • Pancreatic beta-cell biology and insulin regulation[3]
  • Peripheral nerve regeneration using controlled-release biomaterials[4]
  • Production and bioactivity optimization for research supply[2]

How IGF-1 LR3 Is Dosed in Research

Dosing in published studies varies widely depending on the research model, the delivery method, and the biological question being asked — from continuous intravenous infusions in large animal models to controlled local release in nerve conduit studies. Rather than list every number here, check the dosage chart on this page for a clear summary of the doses used in key published studies, and use the calculator to scale or convert units for your own reference purposes. Always consult the original study protocols when designing any research application.[1][5][6]

Mixing and Storing IGF-1 LR3

IGF-1 LR3 is typically supplied as a lyophilized (freeze-dried) powder. To reconstitute it, researchers generally dissolve the powder in sterile, slightly acidic water — commonly 0.1–1% acetic acid or sterile bacteriostatic water — to help the peptide go into solution without denaturing (unfolding and losing activity). Add the liquid slowly down the side of the vial; never shake vigorously. Reconstituted solutions are usually stored at 2–8 °C (standard refrigerator temperature) for short-term use, or frozen at −20 °C for longer storage. Avoid repeated freeze-thaw cycles, as these can degrade the peptide. Always label vials with the date of reconstitution. These are general laboratory handling principles; follow the specific protocols provided by your supplier and institution.

Sources

  1. IGF-1 LR3 does not promote growth in late-gestation growth-restricted fetal sheep. — American journal of physiology. Endocrinology and metabolism, 2025. PMID 39679943.
  2. Recombinant expression of IGF-1 and LR3 IGF-1 fused with xylanase in Pichia pastoris. — Applied microbiology and biotechnology, 2023. PMID 37261455.
  3. Attenuated glucose-stimulated insulin secretion during an acute IGF-1 LR3 infusion into fetal sheep does not persist in isolated islets. — Journal of developmental origins of health and disease, 2023. PMID 37114757.
  4. Revolutionary decellularized Alstroemeria stem-based nerve conduit integrated with GelMA and controlled IGF-1 LR3 release for enhanced rat sciatic nerve regeneration. — International journal of biological macromolecules, 2025. PMID 41015370.
  5. Coronary vascular growth matches IGF-1-stimulated cardiac growth in fetal sheep. — FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 2020. PMID 32573852.
  6. IGF-1 infusion to fetal sheep increases organ growth but not by stimulating nutrient transfer to the fetus. — American journal of physiology. Endocrinology and metabolism, 2021. PMID 33427051.

IGF-1 LR3 FAQ

What is IGF-1 LR3?
IGF-1 LR3 (Long R3 Insulin-like Growth Factor-1) is a synthetic analog of the natural IGF-1 hormone. Two structural modifications give it a much lower affinity for IGF-binding proteins, meaning it stays active in circulation far longer than regular IGF-1. It is used in laboratory and animal research to study growth signaling, organ development, and tissue repair.[1][2]
How does IGF-1 LR3 work?
IGF-1 LR3 binds to the IGF-1 receptor on cell surfaces, triggering internal signals that promote cell growth, division, and protein synthesis. Because its binding protein affinity is very low, it avoids being neutralized quickly in the bloodstream and reaches target receptors more effectively than native IGF-1. This makes it a valuable research tool for studying IGF-1 pathways.[1][5]
What is IGF-1 LR3 used for in research?
Research applications include studying fetal organ and cardiac growth, coronary vascular development, pancreatic beta-cell insulin secretion, and peripheral nerve regeneration. In animal models, it has been infused directly into fetal sheep to explore growth restriction therapies[1][6] and embedded in nerve conduits to promote sciatic nerve repair in rats.[4] It is not approved for human therapeutic use.
How is IGF-1 LR3 dosed?
Doses differ greatly by study design and model. Fetal sheep studies have used continuous intravenous infusions over approximately one week, while nerve regeneration research uses controlled local release from a biomaterial scaffold.[1][4][5] See the dosage chart on this page for specific published values, and use the calculator to work with units. There is no established human dose — this is a research compound only.
How do you reconstitute IGF-1 LR3?
IGF-1 LR3 powder is typically dissolved in sterile, slightly acidic water (such as 0.1% acetic acid or bacteriostatic water) by adding liquid gently down the vial wall — never shake. The reconstituted solution is stored at 2–8 °C for short-term use or frozen at −20 °C for longer storage. Avoid repeated freeze-thaw cycles to preserve activity. Always follow your supplier's specific instructions.
Is IGF-1 LR3 safe?
In the animal studies reviewed, IGF-1 LR3 did not cause overt systemic toxicity — for example, the nerve conduit study in rats reported no systemic toxic effects.[4] However, research also shows it can suppress insulin secretion and reduce circulating amino acids in fetal models.[1][3] IGF-1 LR3 is not approved for human use, and its safety profile in humans has not been established through clinical trials.