Overview
IGF-1 LR3 (Long Arg3 IGF-1) is a synthetic analog of Insulin-like Growth Factor-1 (IGF-1).
Mechanism of Action
IGF-1 LR3 acts via the IGF-1 receptor (IGF1R):
Activates:
- PI3K–AKT pathway → protein synthesis, anti-catabolic
- MAPK pathway → cell proliferation
Effects:
- Muscle hypertrophy
- Satellite cell activation
- Increased nutrient uptake (glucose, amino acids)
Indications
- Severe primary IGF-1 deficiency
- Growth failure in children
- Lean muscle gain
- Fat loss (indirect via nutrient partitioning)
- Enhanced recovery
Dosage
SQ (50 mcg) to be taken once daily after meal, 5 days per week.
- Why 5 days per week? (Receptor Sensitivity Rationale)
This is an important practical concept.
 Receptor Dynamics:
- Continuous IGF-1 exposure → IGF-1 receptor downregulation
- Leads to:
- Reduced signaling response
- Diminishing returns over time
- Using 5 days ON / 2 days OFF:
- Allows receptor resensitization
- Helps maintain anabolic responsiveness
- Reduces risk of tachyphylaxis
Side Effects
Common:
- Hypoglycemia (avoided when taken with / after a meal)
- Water retention / edema
- Headaches
- Fatigue
Contraindications
Avoid in:
- Active or history of cancer
- Diabetes or insulin resistance
- Pediatric / growth disorders (unless medically supervised)
- Pregnancy / breastfeeding
Uncontrolled endocrine disorders
