IGF-1 LR3
A long-acting analog of human IGF-1, designed to be more potent and last longer in the body to support muscle growth.
Common Dosage
20mcg - 50mcg post-workout
Category
Muscle Growth
- Muscle hyperplasia
- Enhanced recovery
- Nutrient shuttling
IGF-1 LR3 (Insulin-like Growth Factor-1 Long Arginine 3) is a synthetic analogue of human IGF-1 with a modified N-terminus (Arg3) and an additional 13-amino-acid sequence that renders it unable to bind IGF-binding proteins in the circulation. This structural change dramatically extends its half-life (20–30 hours vs. ~20 minutes for native IGF-1) and increases its bioavailability at tissue receptors. It was developed as a research tool to study IGF-1 biology and has been extensively used in performance enhancement research.
IGF-1 LR3 binds to the IGF-1 receptor (IGF1R) on muscle cells, activating PI3K/Akt/mTOR signaling pathways that drive both muscle hypertrophy (increased cell size) and hyperplasia (increased cell number — a genuinely unusual effect). By escaping IGF-binding protein sequestration, it delivers prolonged receptor stimulation that promotes protein synthesis, glucose uptake, and satellite cell activation for muscle fiber repair and growth.
- Skeletal muscle hyperplasia research — possibly unique among anabolic peptides
- Post-workout muscle recovery optimization
- Nutrient partitioning enhancement
- Wasting disease and cachexia research
- Growth hormone deficiency supportive therapy research
Bodybuilding Research Community
Among competitive bodybuilders, IGF-1 LR3 is regarded as one of the most potent muscle-building peptides — specifically valued for its purported ability to induce true muscle fiber hyperplasia. Self-reported outcomes of 5–10 lbs of lean mass gain over 4-week cycles at 50–100mcg are common, though placebo effects in self-reporting are substantial.
Recovery Enhancement
Post-workout administration (bilateral injection close to worked muscle groups or systemic subcutaneous) has been associated with significantly accelerated recovery and reduced soreness — consistent with IGF-1's role in muscle satellite cell activation and repair signaling.
- Hypoglycemia risk is significant — IGF-1 has insulin-mimicking activity; co-administration with insulin or in fasted states is dangerous
- Gut distension ('GH gut') at high doses or chronic use — associated with IGF-1's proliferative effects on intestinal smooth muscle
- Theoretical cancer promotion — IGF-1 receptor activation drives cell proliferation; contraindicated with any malignancy history
- Acromegaly-like effects with prolonged high-dose use including jaw growth, organ enlargement
- Headaches, jaw pain, and hypoglycemic episodes are commonly reported side effects
- Extremely short research peptide shelf life — must be used within 3–4 weeks of reconstitution even when refrigerated
- Hypoglycemia
- Gut distension (high dose)