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Original illustration for IGF-1 LR3 research notes: abstract molecular artwork in orange and teal
Original illustration by USA Peptide Vendors; artistic, not a structural model.

Growth & signaling research peptides

IGF-1 LR3 research guide in four steps

83-residue recombinant analogue of human IGF-1 with arginine at position 3 and a 13-residue N-terminal extension.

GrowthLong R3 IGF-1LGF-1 LR3 (Purgo spelling)Updated 2026-11-09

  1. Confirm what IGF-1 LR3 is

    Recombinant 83-residue protein. No PubChem or KEGG record, so CAS, formula and weight are left out; Purgo's listed values could not be verified.

    Verified 2026-11-09 against Francis et al. 1992 (PubMed 1378742). Values we couldn't verify are left out.

  2. Know the proposed mechanism

    The changes were designed to cut binding to IGF-binding proteins, which leaves more free analogue and raised its potency in cell culture. Purgo sells 1mg vials.

    Mechanism map

    Evidence level: Preclinical: cell culture. All mechanism maps

    IGF-1 LR3 mechanism diagramWeak binding to IGF-binding proteins leaves more analogue free to reach the IGF-1 receptor. Targets: IGF-1 receptor. Why it is more potent: Low IGFBP binding → More free analogue. Effect reported: Higher biological potency.IGF-1 LR3 mechanism mapWeak binding to IGF-binding proteins leaves more analogue free to reach the IGF-1receptorIGF-1 LR383-residue IGF-1 analogueIGF-1 receptor[1]Low IGFBP binding[1]More free analogue[1]Higher biological potencycell culture [1]Evidence: Preclinical: cell culture. Numbers in brackets refer to the cited sources.usapeptidevendors.com · Research Use OnlyRECEPTORWHY IT IS MORE POTENTEFFECT REPORTED
    Potency comparisons come from in-vitro assays. Open SVG
    1. Francis GL et al. Novel recombinant fusion protein analogues of insulin-like growth factor (IGF)-I indicate the relative importance of IGF-binding protein and receptor binding for enhanced biological potency. J Mol Endocrinol. 1992;8:213-23.

  3. Compare two documented suppliers

    26 of 112 directory vendors list IGF-1 LR3; 14 name their testing lab.

  4. Verify the lot before use

    1. Purgo sells it as “lGF-1 LR3”. Make sure the COA names the analyte, not just the store label.
    2. 26 of the 112 vendors in our directory list IGF-1 LR3; 14 of those name the lab that tests it.

FAQ

What is IGF-1 LR3?

83-residue recombinant analogue of human IGF-1 with arginine at position 3 and a 13-residue N-terminal extension. The changes were designed to cut binding to IGF-binding proteins, which leaves more free analogue and raised its potency in cell culture. Purgo sells 1mg vials.

Where can US labs buy IGF-1 LR3?

Purgo Labs stocks it as “lGF-1 LR3”; code usapeptidevendors takes 25% off at checkout. This page also lists the best-documented second vendor from our 112-vendor directory.

Is research-grade IGF-1 LR3 for human use?

No. Vendor material is sold for Research Use Only, not for human or veterinary use.