IGF-1 LR3

Long R3 IGF-1 — a chemically modified IGF-1 analog with an arginine substitution at position 3 and a 13-amino-acid N-terminal extension. The modifications dramatically extend half-life from ~20 minutes (native IGF-1) to 20–30 hours, making it pharmacologically distinct.

Activates the IGF-1 receptor with 2–3x potency of native IGF-1 due to reduced binding affinity for IGFBPs (binding proteins that normally inactivate it). Drives satellite cell activation, muscle protein synthesis, and hyperplasia in trained muscle.

Animal data robust for muscle growth and satellite cell activation. Human RCT data is limited — most evidence is from bodybuilding observational use. Bachmeyer cites a 600,000-person observational study finding no causal IGF-1/cancer link; others remain cautious.

Sources: PubMed: IGF-1 LR3

Range

20–50 mcg per injection site

Frequency

Post-workout near trained muscle; eat carbs within 20–30 min

Duration

4–6 week cycles maximum; receptor desensitization is real

Sources: PubMed

Common

• Hypoglycemia if dosed without carbs
• Site soreness
• Joint pain at high doses

Serious / theoretical

• Theoretical cancer risk (IGF-1 permissive for cell replication)
• Avoid in active malignancy or family history
• Acromegalic features at chronic high doses

Sources: PubMed

JD Denham and Castore consensus: post-workout + carbs within 30 min is non-negotiable. Bachmeyer says cancer-IGF-1 link comes from metabolic dysfunction, not the peptide. Tatem rates it inferior to real GH for serious lifters.