Growth Hormone Axis
IGF-1 LR3
Long-acting IGF-1 analog with potent anabolic effects in animals; no human trials and significant hypoglycemia and growth-promotion risks.
Overview
IGF-1 LR3 is an engineered version of insulin-like growth factor-1, the hormone that carries out many of growth hormone's effects. Two changes — an extra 13 amino acids and a single arginine substitution — keep it from being captured by IGF-binding proteins, so far more of it stays active and it lasts roughly a day instead of minutes. In animals and cell culture it strongly promotes muscle protein synthesis and satellite-cell activity. It has never been tested in human trials. Because it acts like insulin and directly drives cell growth, the risks include low blood sugar and theoretical promotion of tumors. It is among the higher-risk compounds in this class.
- Classification
- Recombinant IGF-1 analog (83 aa: 13-aa N-terminal extension plus Glu3→Arg substitution)
- Route
- Subcutaneous
- Half-life
- ~20–30 hours (estimated; not studied in humans)
Mechanism of action
- Escapes binding proteinsReduced IGFBP affinity leaves most of the dose free and active.
- Activates IGF-1RBinds the IGF-1 tyrosine-kinase receptor on muscle and other tissues.
- PI3K/Akt and MAPKTriggers growth and survival signaling cascades inside the cell.
- mTOR protein synthesisAkt-mTOR activation increases muscle protein synthesis.
- Glucose uptakeInsulin-like action drives glucose into cells, lowering blood sugar.
- Muscle hypertrophy (animal data)
- Satellite cell activation
- Lower blood glucose
Researched for
- Muscle growth (animal models)
- Muscle wasting (preclinical)
- Cell-culture bioprocessing
- Wound healing (preclinical)
Research notes
- Original characterization (Francis 1992) showed markedly reduced IGFBP binding and increased bioactivity.
- Rat studies (Tomas 1993) found greater protein deposition than native IGF-1.
- No human pharmacokinetic, efficacy or safety trials have been published.
- IGF-1 signaling is linked epidemiologically to cancer risk (Pollak 2008), supporting strict avoidance with any cancer history.
Reported side effects
- Hypoglycemia (most common)
- Joint pain
- Water retention
- Injection-site reactions
- Suppression of natural GH/IGF-1 axis
Contraindications & cautions
- Any current or prior malignancy
- Insulin-treated diabetes or hypoglycemic disorders
- Untreated diabetic retinopathy
- Pregnancy or breastfeeding
- Significant cardiac disease
Lab monitoring
- Fasting glucose (home monitoring advised)
- HbA1c and fasting insulin
- IGF-1
- Lipid panel and CBC
- Age-appropriate cancer screening
Dosing and pricing for IGF-1 LR3
Dosing references and compound pricing are available to established patients in the secure portal after a medical evaluation.
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