Growth hormone secretagogue
IGF-1 LR3
A long-acting laboratory analogue of insulin-like growth factor 1, sold for muscle growth with almost no human data behind it.
What it is
IGF-1 LR3 (long R3 IGF-1) is human insulin-like growth factor 1 with a 13-amino-acid extension and an arginine substitution. Those changes stop it binding the proteins that normally restrain IGF-1, so it stays active far longer than the natural hormone. It is a laboratory reagent, not a medicine; the approved IGF-1 product is mecasermin, a different molecule used for severe growth failure. It is prohibited in sport.
How it works
- 1
Binds the IGF-1 receptor, which drives cell growth, division and survival.
- 2
Because it escapes IGF-binding proteins, it reaches tissues at far higher free concentrations than natural IGF-1.
- 3
Its extended half-life means sustained rather than pulsatile signalling.
- 4
In animal models it increases protein synthesis and glucose uptake in muscle, and also drives connective-tissue and organ growth.
- 5
It suppresses the body's own growth-hormone output through negative feedback.
What it's studied for
Reported and studied effects
- Increased lean tissue in animal models
- Hypoglycaemia — IGF-1 acts like insulin
- Fluid retention, joint pain and carpal-tunnel symptoms seen in the IGF-1 drug class
- Growth of existing tumours is a theoretically and experimentally supported risk
Research protocol notes
Research context onlyResearch context only — no human protocol exists for LR3. There are no published human dose-ranging studies; schedules circulating online, such as 20–50 micrograms per day with weekly increases, are entirely anecdotal. Any dose carries a real risk of hypoglycaemia.
These figures are described so you can understand what researchers did. They are not a dose, a schedule, or a suggestion — and they are not a substitute for a doctor.
Possible side effects and contraindications
Safety profile
Possible side effects
- Hypoglycaemia, occasionally severe
- Jaw and joint pain, carpal tunnel syndrome
- Swelling and fluid retention
- Headache and injection-site reactions
- Possible promotion of existing cancers
Contraindications and cautions
- Any history of cancer
- Diabetes or impaired glucose handling
- Pregnancy, breastfeeding and childhood
- Retinopathy, which IGF-1 can worsen
- Prohibited in competitive sport
A side-effect list is never complete, and these are not the only situations that warrant caution. Anything unexpected, or anything you are unsure about, should be discussed with a doctor before use.
Evidence assessment
There are no controlled human studies of IGF-1 LR3 itself; what is known comes from animal and cell work plus the behaviour of the related approved drug mecasermin.
References
- 01Long R3 IGF-1 in animal models — PubMed search
- 02Mecasermin (approved IGF-1) safety and effects — PubMed search
- 03World Anti-Doping Agency — Prohibited List
References link to published literature, regulator pages or literature indexes. Where a link points to a search, it collects the peer-reviewed work on that molecule rather than a single study.
Related
Related peptides
Other entries in Growth hormone secretagogue.
Growth hormone secretagogue
CJC-1295
A modified growth-hormone-releasing hormone analogue whose albumin binding gives it an unusually long action. Studied in small human trials; not an approved medicine.
Growth hormone secretagogue
CJC-1295 (no DAC) + Ipamorelin blend
The classic growth-hormone stack in one vial: a GHRH fragment with a secretagogue, unapproved and prohibited in sport.
Growth hormone secretagogue
CJC-1295 (no DAC) / mod GRF 1-29
The short-acting sister of CJC-1295: a GHRH fragment that produces brief growth-hormone pulses instead of sustained elevation.