IGF-1 LR3
What IGF-1 LR3 is
IGF-1 LR3 is a modified analogue of insulin-like growth factor 1. Two changes distinguish it from the native molecule: an arginine substituted at position 3, and a 13 amino acid extension at the N-terminus. The name encodes both, Long R3.
Those modifications exist for one purpose. Native IGF-1 in circulation is almost entirely bound to IGF binding proteins, which regulate its availability. The R3 substitution sharply reduces that binding affinity, so the analogue remains free for considerably longer.
At a glance
| Class | Long-arg3 IGF-1 analogue |
|---|---|
| Modifications | Arg at position 3, 13-residue N-terminal extension |
| Key property | Reduced IGF binding protein affinity |
| Presentation | Lyophilised powder |
| Reported half-life | Longer than native IGF-1 |
| Storage | 2 to 8 °C, avoid repeated freeze-thaw |
How it relates to growth hormone
IGF-1 is downstream of growth hormone. GH acts on the liver and other tissues, which respond by producing IGF-1, and much of what is attributed to growth hormone is mediated through it.
That places IGF-1 LR3 in a different position from the secretagogues in this reference. Ipamorelin, sermorelin, CJC-1295 and MK-677 all act upstream, prompting the body's own GH release. IGF-1 LR3 supplies the downstream molecule directly, bypassing that chain.
| Approach | Compounds | Acts |
|---|---|---|
| Secretagogue | Ipamorelin, sermorelin, CJC-1295, MK-677 | Upstream of GH release |
| Growth hormone | HGH | The hormone itself |
| IGF-1 analogue | IGF-1 LR3 | Downstream mediator |
Handling
IGF-1 LR3 is more sensitive to freeze-thaw than most compounds here, and the guidance to avoid repeated cycles is emphasised rather than routine. Plan the reconstituted volume around actual use rather than convenience.
Bring the vial to room temperature before adding diluent. Run the liquid down the inside wall of the glass, never into the powder. Let it dissolve unaided and do not shake. The solution should be clear and colourless.
Some suppliers specify a particular diluent for IGF-1 analogues rather than standard bacteriostatic water. Follow the batch documentation where it differs from general practice; the specification for the material in hand always governs.
Storage
Sealed and lyophilised, 2 to 8 °C away from light. Reconstituted, refrigerate upright and dark and do not freeze. Where bacteriostatic water is the diluent, the 28 day window from first puncture applies as usual.
Frequently asked
What does LR3 mean? Long R3. "R3" is the arginine substitution at position 3; "Long" is the 13 amino acid N-terminal extension.
Is it the same as IGF-1? No. Native IGF-1 binds readily to IGF binding proteins. The LR3 analogue is modified specifically to reduce that, which changes how long it stays free in circulation.
Is it a growth hormone? No. It is downstream of growth hormone rather than being one.
Can it be combined with a secretagogue? They act at different points in the same axis, which is why the combination appears in the literature. Reconstitute separately and keep concentrations tracked independently.