IGF-1 LR3

Growth Hormone Secretagogues

aka Long R3 IGF-1 · LR3 IGF-1 · Long [Arg3] IGF-1

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Formula

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MW (Da)

Half-life

~20–30 hours

Saves

0

Overview

IGF-1 LR3 is a synthetic 83-amino-acid analog of IGF-1 with an arginine substitution at position 3 plus a 13-amino-acid N-terminal extension. It is predominantly a research reagent; the retrieved literature did not identify a substantial clinical efficacy program in humans specific to LR3.

Mechanism

The two sequence modifications sharply reduce affinity for IGF-binding proteins, especially IGFBP-3, which is one reason LR3 remains more bioavailable than native IGF-1. A cited biochemical study reported that [long Arg3]IGF-1 bound IGFBP-3 with less than 0.2% of the potency of IGF-1 in that assay system. The downstream signaling can therefore be understood as relatively persistent IGF1R agonism, with the expected PI3K-AKT-mTOR and MAPK/ERK consequences.

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Reported benefits

Preclinical trophic and growth effects

Animal and tissue studies support trophic or proliferative effects, including preferential intestinal delivery and activity in myoblast or growth models. Human therapeutic effects specific to LR3 have not been well elucidated in the sources reviewed.

[lr3-intestinal-delivery]

preclinical

Reduced IGFBP-3 binding (mechanism)

[long Arg3]IGF-1 bound IGFBP-3 with less than 0.2% of the potency of IGF-1, supporting greater free-fraction availability for IGF1R signaling.

[salahifar-igfbp3]

preclinical

Reported side effects

Theoretical mitogenic and metabolic concerns
anecdotal
Human incidence data are unavailable. Amplified IGF signaling raises theoretical concerns around hypoglycemia, excessive tissue growth, and tumor promotion.
Reduced food intake and growth at high rat doses
preclinical
In one rat study, 180 mcg/kg/day continuous infusion reduced food intake, weight gain, and several circulating IGF-axis markers.

Dosing notes

No standardized human research dose was identified. Published preclinical work includes continuous infusion paradigms such as 180 mcg/kg/day. Many commercial datasheets present the peptide primarily as a recombinant protein for cell-culture systems rather than a drug-development product.

Research use only. Information on this page is editorial reference, not medical or dosing advice. Always consult qualified medical guidance before use.

Storage

A recombinant LR3 IGF-1 datasheet recommends storage of the lyophilized protein at -20 to -70 C. After reconstitution, aliquot and store at -20 to -70 C for up to roughly 3 months; avoid repeated freeze-thaw cycles.

Vendors carrying IGF-1 LR3

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References

[rd-systems-lr3]
Recombinant Human LR3 IGF-I / IGF-1 GMP Protein, CF (datasheet)
R&D Systems · R&D Systems product datasheet
Source
[lr3-intestinal-delivery]
Preferential intestinal delivery of Long-Arg3 IGF-1
Authors per Endocrinology paper · Endocrinology
Source
[rat-lr3-infusion]
Long [R3] IGF-1 continuous infusion reduces growth and plasma markers in rats
Authors per Journal of Endocrinology · Journal of Endocrinology
Source
[salahifar-igfbp3]
IGFBP-3 binding affinity of [long Arg3]IGF-1 (Salahifar et al.)
Salahifar H et al. · 1997 · PubMed
Source
[novus-lr3]
LR3 IGF-I recombinant protein datasheet (NBP2-61314)
Novus Biologicals · Novus Biologicals datasheet
Source