Growth

IGF-1 LR3

Polypeptide · Long R3 IGF-1 analogue · 83 amino acids

FDA · CATEGORY 2 (2023)

Half-life

~1 days

Long

minsdays

Route

SubQ injection

Evidence

Preclinical only

Risk

Elevated

Overview

Known for

Long-acting insulin-like growth factor. Directly stimulates muscle growth and cell proliferation. More potent than standard IGF-1 (longer half-life). Promotes hyperplasia (new muscle cell creation) not just hypertrophy.

Mechanism

Modified IGF-1 — downstream effector of GH. Directly drives muscle growth, cell proliferation, protein synthesis. Bypasses GH entirely.

Key facts

Format
Lyophilized powder
Mechanism targets
Classification
Secondary
Supply & nature
ExogenousExogenous
FDA category
Category 2 (2023)

Evidence & standing

Evidence base
Preclinical only
Risk level
Elevated
Best studies
5 references
  • Francis et al. (1992) J Mol Endocrinol 8:213-23 — LR3 characterization
  • Pharmaceutically, mecasermin (Increlex) is FDA-approved rIGF-1 for severe GHD
  • LR3 variant is research-only — longer half-life than native IGF-1
  • NOT FDA APPROVED (LR3 specifically)
  • ⚠️ Hypoglycemia risk well documented

Dosage & protocol

Typical dose
20-80mcg/day
Research range
20–100 µg
Cycle
4 weeks on / 4 weeks off
Onset
10 days first effects
Full effect
35 days
Half-life
~20-30h
~20-30 hours (LR3 modification extends half-life vs native IGF-1 at ~12 min)
Protocol

20-80mcg/day SubQ or IM (bilateral into target muscles). Most use 40-60mcg/day. Cycle 4-6 weeks on, 4-6 off.

Time to effects

EARLY: 1-2 weeks

FULL: 4-6 weeks

Week 1: Pumps during training, potential hypoglycaemia (have glucose source ready). Muscle fullness.

Week 2-4: Noticeable muscle growth and recovery. Localised growth in injected muscle groups.

Week 4-6: Significant body composition changes. New muscle cell creation (hyperplasia) — permanent gains.

⚠️ Cycle 4-6 weeks on, 4-6 off. Effects are relatively fast due to direct growth factor activity. Monitor blood glucose closely.

Recommended vial
  • 1mg vials

At 50mcg/day, 1mg = 20 days ✓. 0.1mg = 2 days (impractical). IGF-1 is FRAGILE (2-4 wk shelf life). 1mg is the only practical choice.

Reference figures only

Dosing reflects published laboratory protocols and is not guidance for use in any living subject.

Safety

Reversibility
Unknown
Side effects

Hypoglycaemia (SIGNIFICANT — 15-25%), joint pain, headache, jaw/hand growth (chronic use), organ growth

Interactions

Insulin (synergistic hypoglycaemia risk — DANGEROUS), anti-diabetics, other growth factors

Handle with research caution

⚠️ CONTRAINDICATED in any personal or family history of cancer — IGF-1 is a potent growth factor strongly associated with cancer risk

  • Caution combining with exogenous HGH (compounded growth factor load, insulin resistance)
  • Do NOT use on days you inject MGF/PEG-MGF (alternate — MGF for repair days, IGF-1 for growth days)
  • ⚠️ Monitor blood glucose — can cause hypoglycaemia

Storage & handling

Lyophilised
12–24 months
2–8°C
Reconstituted
2–4 weeks
2–8°C

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