IGF-1 LR3

Overview

IGF-1 LR3 is an 83-amino-acid modified IGF-1 analog with a 13-residue N-terminal extension (MFPAMPLSSLFVN) and an Arg-3 substitution. These modifications reduce binding to IGF binding proteins (IGFBPs), extending effective half-life and increasing tissue bioavailability relative to native IGF-1. It is a research/cell-culture reagent and is NOT FDA-approved for any human use. Do not confuse with mecasermin (Increlex), which is recombinant human IGF-1 and IS FDA-approved for severe primary IGF-1 deficiency.

Mechanism of Action

IGF-1 LR3 binds the IGF-1 receptor (IGF-1R) with high affinity and drives PI3K/Akt and MAPK signaling, producing anabolic and mitogenic effects including muscle protein synthesis, satellite-cell activation, and broad cell proliferation. The Arg-3 substitution and N-terminal extension lower IGFBP affinity, so more free peptide reaches tissue receptors and the effective half-life is extended relative to native IGF-1 (which clears in minutes).

Research Summary

Francis et al. (J Mol Endocrinol 1992; PMID 1378742) characterized LR3-IGF-1 as a fusion analog whose enhanced biological potency derives from reduced IGFBP binding; in IGFBP-free cell systems LR3 was actually LESS potent than native IGF-1, underscoring that the 'potency' is really reduced sequestration rather than intrinsically stronger receptor activation. Tomas (Growth Horm IGF Res 2001; PMID 11472075) infused LR(3)IGF-I into food-restricted rats and found it preserved body weight and nitrogen retention but did NOT conserve skeletal muscle protein — which contradicts the common 'potent muscle builder' framing from preclinical literature alone. There are no controlled human trials supporting bodybuilding use. Epidemiologic and mechanistic work reviewed by Grimberg (Cancer Biol Ther 2003; PMID 14688466) links elevated IGF-1 axis activity to breast, prostate, and colorectal cancer risk, so chronic systemic LR3 exposure carries a concrete — not merely theoretical — tumorigenesis concern. IGF-1 and its analogs are banned at all times under the WADA Code.

Vendors selling IGF-1 LR3

Scored vendors carrying IGF-1 LR3, ranked by trust grade. Grades are computed from indexed Certificates of Analysis. Full $/mg pricing is on the comparison page.

Prescribers who offer IGF-1 LR3

27 prescribers in our directory work with IGF-1 LR3, each confirmed from their own website. Peptides like IGF-1 LR3 require a prescription from a licensed provider — telehealth options are available.

Reported Side Effects

• Hypoglycemia (real risk — IGF-1 has insulin-like activity)
• Joint pain and arthralgia
• Acromegaly-like soft-tissue changes with prolonged high-dose use (jaw, hands, feet)
• Gut/visceral overgrowth reported with chronic supraphysiologic exposure
• Injection site irritation
• Unknown long-term tumorigenesis risk (IGF-1 pathway drives multiple cancers)

Compare IGF-1 LR3 with Others

Research References

• 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 (Francis et al., J Mol Endocrinol) (1992)
• Insulin-like growth factor-I (IGF-I) analogue, LR(3)IGF-I, ameliorates the loss of body weight but not of skeletal muscle during food restriction (Tomas, Growth Horm IGF Res) (2001)
• Mechanisms by which IGF-I May Promote Cancer (Grimberg, Cancer Biol Ther) — review of IGF-1 axis and tumorigenesis (2003)

Frequently asked questions

Has IGF-1 LR3 been independently lab-tested?

Disclosed Labs has collected 43 Certificates of Analysis (COA) for IGF-1 LR3 from 9 independent testing labs. 23 vendors have submitted material for testing. Products average 98.7% tested purity across the corpus. Full testing data is available at https://www.disclosedlabs.com/peptides/igf-1-lr3/testing.

What is the average purity of IGF-1 LR3 on the market?

Based on 43 COAs analyzed by Disclosed Labs, IGF-1 LR3 products average 98.7% (±1.4%) tested purity. Individual vendor results vary; see per-vendor COA data at https://www.disclosedlabs.com/peptides/igf-1-lr3/coas.

Which labs have tested IGF-1 LR3?

Independent labs that have tested IGF-1 LR3 include: ILS Labs (Grade A). Full lab credibility grades and profiles are at https://www.disclosedlabs.com/labs.

Where can researchers source IGF-1 LR3?

8 vendors with Disclosed Labs trust grades currently list IGF-1 LR3, including Ion Peptide, Synthesis Peptides, Skye Peptides. Compare live prices and lab-verified COAs at https://www.disclosedlabs.com/prices/igf-1-lr3.

Which prescribers offer IGF-1 LR3 with a prescription?

27 prescribers in the Disclosed Labs directory work with IGF-1 LR3, each confirmed from their own website, with telehealth options available. IGF-1 LR3 requires a prescription from a licensed provider. Browse them at https://www.disclosedlabs.com/prescribers?peptide=IGF-1%20LR3.

How does IGF-1 LR3 work?

IGF-1 LR3 binds the IGF-1 receptor (IGF-1R) with high affinity and drives PI3K/Akt and MAPK signaling, producing anabolic and mitogenic effects including muscle protein synthesis, satellite-cell activation, and broad cell proliferation. The Arg-3 substitution and N-terminal extension lower IGFBP affinity, so more free peptide reaches tissue receptors and the effective half-life is extended relative to native IGF-1 (which clears in minutes).

What does the research say about IGF-1 LR3?

Francis et al. (J Mol Endocrinol 1992; PMID 1378742) characterized LR3-IGF-1 as a fusion analog whose enhanced biological potency derives from reduced IGFBP binding; in IGFBP-free cell systems LR3 was actually LESS potent than native IGF-1, underscoring that the 'potency' is really reduced sequestration rather than intrinsically stronger receptor activation. Tomas (Growth Horm IGF Res 2001; PMID 11472075) infused LR(3)IGF-I into food-restricted rats and found it preserved body weight and nitrogen retention but did NOT conserve skeletal muscle protein — which contradicts the common 'potent muscle builder' framing from preclinical literature alone. There are no controlled human trials supporting bodybuilding use. Epidemiologic and mechanistic work reviewed by Grimberg (Cancer Biol Ther 2003; PMID 14688466) links elevated IGF-1 axis activity to breast, prostate, and colorectal cancer risk, so chronic systemic LR3 exposure carries a concrete — not merely theoretical — tumorigenesis concern. IGF-1 and its analogs are banned at all times under the WADA Code.