IGF-1 LR3
Aliases: Long R3 IGF-1 · LR3IGF-I
Last verified: 2026-09-23
The short version
IGF-1 LR3 is an anabolic signaling molecule with serious theoretical risks: the IGF-1 pathway is directly involved in cell growth, so chronic exposure is linked to cancer risk (acromegaly, where GH/IGF-1 is chronically high, associates with higher rates of adenomas and carcinomas). There is virtually no controlled human data for the LR3 form; the sponsor is anecdote about hypertrophy. Treat it as a high-risk, unproven substance.
Identity & type
- Molecular type
- analog
- Sequence / structure
- 83 aa, Arg3 + N-terminalna ekstenzija IGF-1
- Molecular weight
- ~9111 Da
- Origin
- Long R3 analog of insulin-like growth factor 1 — designed to avoid binding to IGF binding proteins and extend half-life.
Mechanism of action
Activates the IGF-1 receptor → PI3K/Akt/mTOR and MAPK pathways → protein synthesis, satellite-cell proliferation, hyperplasia.
not confirmed in humans
Dosing & routes
Official / clinical context
No approved official document exists for IGF-1 LR3. Any protocols mentioned are to be read as information, not as a recommendation.
Regulator-approved labeling and published study designs — never a recommendation.
Community-reported practice
20–100 mcg SC once daily post-workout, locally or systemically; ~4-week cycles. Users report pronounced "pump", hypertrophy in trained muscles and faster recovery; it is considered one of the most potent but also riskiest community peptides (hypoglycemia, theoretical growth of existing tumors).
Unverified self-reports. Not medical advice. Not endorsement.
Expected effects (community)
Users report pronounced "pump", hypertrophy in trained muscles and faster recovery; it is considered one of the most potent but also riskiest community peptides (hypoglycemia, theoretical growth of existing tumors).
Protocol — official vs community
Official / label
No approved product. The approved IGF-1 (mecasermin) dosed 0.04–0.12 mg/kg BID — a different molecule and purpose.
Duration: —
LR3 is an IGF-1 analogue with extended half-life and IGF-binding-protein escape — engineered beyond anything studied chronically in humans.
Community (anecdotal)
20–100 mcg SC daily, often post-workout in site-specific or systemic patterns.
- Cycle:
- 4–8 weeks — deliberately short.
- Break:
- 4+ weeks; longer between cycles than on them is the norm.
Short cycles exist for one reason: IGF-1 receptor desensitization and the general rule that chronic IGF-1 elevation trades growth for cancer risk.
Human evidence
Almost none for the LR3 form; natural IGF-1 (mecasermin) is approved only for severe deficiencies and carries strict warnings.
Preclinical evidence
Preclinical research only; no clinical development for this variant. (FDA-approved Mecasermin is plain rhIGF-1.)
Known risks
- Hypoglycemia (potent insulin-like effect)characterized
- Theoretical cancer risk of chronic IGF-1 exposuretheoretical
- Organ growth, carcinoid syndrome (reports)theoretical
Teal: characterized in clinical/labeling contexts. Amber: theoretical or reported outside controlled settings.
Unknowns & evidence gaps
- Human pharmacokinetics of the LR3 form
- Long-term safety of any exogenous IGF-1 therapy
Frequently asked questions
References
- Pollak M., IGF-1 and neoplasia (Nature Reviews Cancer, 2008)