IGF-1 LR3

Description

IGF-1 LR3 (Insulin-like Growth Factor 1, Long Arg3) is an 83-amino acid analog of human IGF-1 engineered for extended biological activity. The “LR3” designation refers to an arginine substitution at position 3 and a 13-amino acid N-terminal extension — modifications that reduce binding to IGF-binding proteins and extend its active half-life from approximately 12 minutes (native IGF-1) to 20-30 hours.

Research Profile

Unlike growth hormone secretagogues that stimulate GH production upstream, IGF-1 LR3 acts directly at the tissue level. It binds the IGF-1 receptor (IGF-1R) to activate PI3K/Akt and MAPK signaling cascades — pathways directly involved in cell proliferation, differentiation, and survival. This downstream mechanism means IGF-1 LR3 operates independently of pituitary function.

Key Research Areas

• Skeletal muscle hypertrophy through satellite cell activation
• Cell proliferation and tissue growth signaling
• Glucose uptake and metabolic regulation
• Neuroprotective and neurotrophic effects
• Wound healing acceleration

Specifications

Type	Modified IGF-1 analog
Molecular Weight	9117.5 g/mol
Purity	≥99% (HPLC verified)
Form	Lyophilized powder
Quantity	1mg per vial
Storage	-20°C pre-reconstitution / 2-8°C post-reconstitution

Related Research Peptides

IGF-1 LR3 is often studied in the context of the broader GH/IGF axis. See CJC-1295 and Ipamorelin for upstream GH stimulation. Complete comparison at our muscle growth peptides guide.

Research Dosage Protocols

IGF-1 LR3 requires careful handling during reconstitution — the peptide is extremely potent and typical research doses are in the 20–100mcg range per administration. A 1mg vial reconstituted in 1mL of 0.1% acetic acid (preferred over bacteriostatic water to prevent aggregation) yields 1,000mcg/mL, meaning most research doses are in the 0.02–0.1mL range. Storage is critical: IGF-1 LR3 degrades rapidly at room temperature and must be kept at 2–8°C after reconstitution with a working window of 2–3 weeks. Acetic acid carrier solutions should be buffered with saline before injection to avoid tissue irritation in animal models.

Frequently Asked Questions

Why does the LR3 modification matter compared to native IGF-1?

Native IGF-1 is rapidly bound by insulin-like growth factor binding proteins (IGFBPs) in circulation — IGFBP-3 in particular sequesters roughly 80–90% of circulating IGF-1, limiting its bioavailability. The LR3 modification replaces the first three amino acids (glutamate-alanine-proline, Glu-Ala-Pro) at the N-terminus with a 13-amino acid extension and substitutes arginine for glutamate-3. These changes reduce IGFBP binding affinity by more than 1,000-fold without compromising receptor binding. The result is a variant that remains bioactive in circulation far longer and at much higher effective concentrations than native IGF-1 — which is exactly what makes it useful for research.

What is the half-life of IGF-1 LR3 compared to native IGF-1?

Native IGF-1’s biological half-life is approximately 12–15 hours when bound to IGFBP-3/ALS ternary complexes, but free unbound IGF-1 clears within minutes. IGF-1 LR3’s reduced IGFBP binding means more remains in the free, bioactive form — its effective half-life in research models is approximately 20–30 hours. This extended biological activity per dose is the primary reason IGF-1 LR3 is preferred over native recombinant IGF-1 for research. Fewer administrations are needed to maintain elevated IGF-1 signaling, and the reduced IGFBP binding makes plasma concentration measurements simpler to interpret.

How does reduced IGFBP binding affect research study design?

In native IGF-1 studies, interpreting plasma IGF-1 levels requires accounting for IGFBP-3 and acid-labile subunit (ALS) concentrations — a complex analysis. With IGF-1 LR3, less is sequestered by binding proteins, so more of the measured peptide is functionally active. This simplifies correlating plasma levels to biological effects. The tradeoff is that IGF-1 LR3’s IGFBP resistance means the natural buffering mechanisms that prevent hypoglycemia from IGF-1 are partially bypassed. Research designs must account for this: hypoglycemic effects are more pronounced and more rapid with LR3 versus native IGF-1 at equivalent total doses.

How do I reconstitute a 1mg vial of IGF-1 LR3 given the small volumes involved?

Add 1mL of 0.1% acetic acid (preferred) or bacteriostatic water to the 1mg vial. This gives 1,000mcg/mL — the highest practical working concentration for dose accuracy. For a 50mcg research dose, you’ll draw 0.05mL (5 units on a U-100 syringe). For a 20mcg dose, 0.02mL (2 units). The small volumes involved mean syringe selection matters — use a U-100 insulin syringe rather than a standard 1mL syringe, as the graduation marks on an insulin syringe allow precise 1-unit (10mcg) resolution. Confirm you’re reading syringe units correctly before proceeding.