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IGF-1 LR3

A modified version of IGF-1 with extended half-life and reduced IGF binding protein affinity, used for muscle growth.

EmergingLimited Data

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This information is for educational purposes. Peptide therapy should be guided by a licensed healthcare provider. Connect with a Noho clinician

What is IGF-1 LR3?

IGF-1 LR3 is a modified form of insulin-like growth factor 1 with an arginine substitution at position 3 and a 13-amino acid N-terminal extension. These modifications dramatically reduce binding to IGF binding proteins (IGFBPs), increasing its bioavailability and half-life from ~15 minutes to ~20 hours. It is primarily used in research and by bodybuilders for muscle growth.

Why People Talk About It

Enhanced muscle growth (hyperplasia)

Emerging

Extended IGF-1 activity vs native IGF-1

Moderate

Recovery from training

Emerging

How It Works

IGF-1 LR3 is a supercharged version of the body's main growth signal. It promotes muscle cell growth and even the creation of new muscle cells, while lasting much longer in the body than natural IGF-1.

Common Questions

Safety Information

Important Safety Notes

Common Side Effects

HypoglycemiaJoint painGut growth (with chronic use)Water retention

Cautions

  • Significant hypoglycemia risk
  • May promote growth of existing tumors
  • Not FDA-approved
  • Organ growth with chronic use

What We Don't Know

Long-term safety is poorly characterized. Theoretical cancer risk from chronic IGF-1R activation.

Published Research

20 studies

The role of the insulin-like growth factor 1 (IGF-1) in skeletal muscle physiology

ReviewPMID: 17354613

Type I insulin-like growth factor receptor signaling in skeletal muscle regeneration and hypertrophy

ReviewPMID: 17947802

IGF-1 LR3 does not promote growth in late-gestation growth-restricted fetal sheep

PreclinicalPMID: 39679943

Revolutionary decellularized Alstroemeria stem-based nerve conduit integrated with GelMA and controlled IGF-1 LR3 release for enhanced rat sciatic nerve regeneration

PreclinicalPMID: 41015370

Attenuated glucose-stimulated insulin secretion during an acute IGF-1 LR3 infusion into fetal sheep does not persist in isolated islets

PreclinicalPMID: 37114757

Impaired muscle regeneration and myoblast differentiation in mice with a muscle-specific KO of IGF-IR

PreclinicalPMID: 20458740

Anabolic effects of insulin-like growth factor-I (IGF-I) and an IGF-I variant in normal female rats.

PreclinicalPMID: 8371075

IGF-I variants which bind poorly to IGF-binding proteins show more potent and prolonged hypoglycaemic action than native IGF-I in pigs and marmoset monkeys.

PreclinicalPMID: 9415072

Superior potency of infused IGF-I analogues which bind poorly to IGF-binding proteins is maintained when administered by injection.

PreclinicalPMID: 8708565

Insulin-like growth factor-I and more potent variants restore growth of diabetic rats without inducing all characteristic insulin effects.

PreclinicalPMID: 7683875

Long [R3] insulin-like growth factor-I reduces growth, plasma growth hormone, IGF binding protein-3 and endogenous IGF-I concentrations in pigs.

PreclinicalPMID: 9488001

Prolonged administration of IGF peptides enhances growth of gastrointestinal tissues in normal rats.

PreclinicalPMID: 7912894

Treatment with IGF-I peptides improves function of the remnant gut following small bowel resection in rats.

PreclinicalPMID: 7803042

Preferential intestinal delivery of long[Arg3] insulin-like growth factor (LR3IGF-I) over IGF-I in preweaning and adult rats.

PreclinicalPMID: 12697696

Transport of circulating IGF-I and LR3IGF-I from blood to extracellular wound fluid sites in rats.

PreclinicalPMID: 10607940

Effects of insulin-like growth factor-I and LR3IGF-I on regional blood flow in normal rats.

PreclinicalPMID: 9415069

The role of insulin-like growth factors in small intestinal cell growth and development.

ReviewPMID: 10226789

Intranasal long R3 insulin-like growth factor-1 treatment promotes amyloid plaque remodeling in cerebral cortex but fails to preserve cognitive function in male 5XFAD mice.

PreclinicalPMID: 39610283

Insulin-like growth factor-I and analogues increase growth in artificially-reared neonatal pigs.

PreclinicalPMID: 12067429

Effects of chronic renal failure on plasma clearance of insulin-like growth factor I, des-(1-3)IGF-I, and LR3IGF-I.

PreclinicalPMID: 8897852

Always consult a qualified clinician

This information is for educational purposes. Peptide therapy should be guided by a licensed healthcare provider. Connect with a Noho clinician

Related Peptides

Quick Facts

Class
Growth Factor Analogue
Evidence
Emerging
Safety
Limited Data
Updated
Mar 2026
Citations
20PubMed

Also known as

Long R3 IGF-1Long Arginine IGF-1

Tags

Growth FactorMuscle GrowthPerformance

Related Goals

Evidence Score

Overall Confidence40%

Clinical Trials

View Clinical Trials

Links to ClinicalTrials.gov for reference. Listing does not imply endorsement.

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