IGF-1 LR3
IGF-1 LR3 is a research reagent. No dedicated human trial exists. Low blood glucose is the main acute risk.
Checked by the PU Research editorial team — evidence-graded against primary sources. Last check: 23 July 2026. Sources: 3. Who checks this
Sport prohibition notice. WADA prohibits GHRH analogs and growth hormone secretagogues under section S2.2.4. Seven of the eight compounds in this category fall under that section. IGF-1 LR3 falls under S2, and its insulin cross-activity also relates to S4. Check the live WADA list before any decision that involves competition.
01Identity & Classification
IGF-1 LR3 means Long R3 IGF-1. It is an 83-amino-acid analog of native IGF-1.
Two changes define it:
- An arginine replaces a glutamic acid at position 3.
- A 13-residue extension sits at the N-terminus.
It is a research reagent.
02Mechanism: How It Works
The changes decrease binding to IGF-binding proteins by about 1,000-fold. This extends the half-life.
The molecule keeps full agonism at the IGF-1 receptor. It activates the PI3K/Akt/mTOR pathway and the Ras/MAPK pathway.
It also cross-reacts with insulin receptors and hybrid receptors. That cross-reaction lowers blood glucose.
03Research Findings
Evidence tier: preclinical only.
Francis et al. (1992) characterized the decreased binding to IGF-binding proteins.
Conlon and Tomas (1995) showed organ-growth stimulation in the guinea pig.
Evidence limit — read this before any other claim. No dedicated human trial of IGF-1 LR3 exists. Every dosing figure and every safety figure in circulation is an extrapolation from a different molecule. The approved native analog is mecasermin (Increlex). Mecasermin is not IGF-1 LR3.
04Reported Dosing & Delivery
No high-authority human dosing exists. Vendors sell it as a research chemical only.
05Pharmacokinetics & Timing
The half-life is about 20 to 30 hours in animal models. No human figure exists.
06Interactions & Combinations
An additive risk of low blood glucose exists with insulin and with an insulin secretagogue. The mechanism supports this risk directly.
Compare with MOTS-c, which shares a glucose-lowering concern.
07Safety & Contraindications
Low blood glucose is the primary acute risk.
Two further concerns exist:
- A theoretical and epidemiologic cancer-promotion risk, through the IGF-1 receptor.
- Organ overgrowth similar to acromegaly, with chronic exposure.
No human safety trial exists.
08Monitoring & Biomarkers
- Glucose.
- IGF-1.
09Regulatory Status
No regulator approves IGF-1 LR3. It is a research chemical.
WADA prohibits growth factors under S2. The insulin cross-activity also relates to section S4. See the WADA prohibited list status.
10Works Cited
- 01Francis GL, et al. Biochemical Journal, 1992. PMID 1601853. View source →
- 02Conlon MA, Tomas FM. Journal of Endocrinology, 1995. PMID 7561636. View source →
- 03WADA 2025 Prohibited List, section S2. View source →
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