IGF-1 LR3

Overview

IGF-1 LR3 is a synthetic, lengthened analog of human insulin-like growth factor 1 (IGF-1): an 83-amino-acid version with an N-terminal extension and an arginine substitution at position 3 that greatly lowers its binding to IGF-binding proteins, giving it a much longer active half-life than native IGF-1. It activates the IGF-1 receptor and downstream PI3K/Akt/mTOR signaling that drives protein synthesis and cell growth. It is not approved for human therapeutic use; it is sold as a research reagent and used in laboratory cell culture, and human data on the marketed muscle-building and fat-loss claims are essentially absent. Because it is a systemic growth factor, theoretical risks include effects on blood glucose and concerns about stimulating growth of existing abnormal cells.

Commonly Reported Uses

These are uses commonly discussed or marketed by users and vendors — not a list of proven or approved benefits, and not a recommendation.

• Laboratory cell-culture and research reagent (its actual established use; not a human therapeutic)
• Muscle growth and hypertrophy (marketed claim; human evidence essentially absent)
• Fat loss / body recomposition (marketed claim; human evidence absent)
• Recovery and 'nutrient partitioning' (marketed claim; not an approved use)

What to Track

Data points you and your clinician might monitor. For observation only — not a diagnostic protocol.

• Labs — fasting glucose and fasting insulin, since IGF-1-receptor activation overlaps insulin signaling and can lower blood sugar
• InBody/DEXA — skeletal muscle mass and body-fat % against a baseline
• Smart scale — weight and body-fat % trend
• Subjective daily check-ins — hypoglycemia symptoms, energy, tolerability
• WHOOP — recovery score and HRV trend

Sources & References

1. [1]IGF-1 LR3 — Wikipedia
2. [2]IGF-1 and the World Anti-Doping Agency Prohibited List — USADA