IGF-1 LR3
Long-acting IGF-1 analog
An extended half-life IGF-1 variant studied for direct anabolic and cell-proliferation signaling downstream of GH.
How it works
IGF-1 LR3 is a modified version of insulin-like growth factor 1, engineered with reduced affinity for IGF binding proteins. In normal physiology, these binding proteins quickly clear circulating IGF-1, but the modification in LR3 substantially extends its circulating half-life, allowing sustained receptor engagement.
Once bound to the IGF-1 receptor, it activates downstream signaling through the PI3K/Akt and mTOR pathways, both of which are central to protein synthesis and cell growth. Because this sits downstream of growth hormone itself, IGF-1 LR3 is studied as a more direct anabolic signal than GH secretagogues.
In vitro and animal research report increased satellite cell activity, a process linked to muscle fiber repair and hyperplasia, alongside marked increases in overall protein synthesis rates. Because IGF-1 signaling overlaps with insulin receptor pathways, hypoglycemia is the most frequently reported acute effect in the literature.
What research has shown
In vitro and animal data show marked increases in protein synthesis, satellite cell activity and muscle hyperplasia markers.
Reported ranges in the literature
Low end
20 to 30 mcg daily
Optimal
40 to 50 mcg daily
High end
80 to 100 mcg daily, short blocks only
Frequency reported in the literature: Daily, 4 weeks on / 4 weeks off in most research designs. Note: Hypoglycemia risk is the most reported acute effect in the literature.
Frequently asked questions
What is IGF-1 LR3?
IGF-1 LR3 is a long-acting analog of insulin-like growth factor 1, studied for its direct anabolic signaling through the IGF-1 receptor and mTOR pathway.
How does IGF-1 LR3 differ from GH secretagogues?
GH secretagogues stimulate the pituitary to raise endogenous GH, which then raises IGF-1 indirectly. IGF-1 LR3 acts directly on the IGF-1 receptor, bypassing that upstream step.
What does the research show?
In vitro and animal data report marked increases in protein synthesis, satellite cell activity, and markers of muscle hyperplasia.
What is the most reported acute effect?
Hypoglycemia is the most consistently reported acute effect in the literature, attributed to overlap between IGF-1 and insulin receptor signaling.
How long are research blocks typically?
Most research designs describe short cycles of around 4 weeks on, followed by 4 weeks off, reflecting concerns about receptor downregulation and metabolic effects.
Related compounds
Further reading
Research use only
All content on this page is general reference information for laboratory research contexts. It is not medical advice, is not intended to direct human use, and does not replace guidance from a licensed healthcare professional. Not for human consumption. Must be 18+.