IGF-1 LR3

Also known as: Long R3 IGF-1, LR3-IGF-1

Wellness

In plain English

IGF-1 LR3 is a modified, longer-lasting version of insulin-like growth factor 1 (IGF-1), the hormone through which much of growth hormone's growth-promoting action occurs. It is essentially a laboratory research reagent; it has no approved medical use as a stand-alone therapy and no completed human trials. Because IGF-1 signaling drives cell growth, there are real theoretical safety concerns (including low blood sugar and cancer-related risks), and it should be regarded as investigational.

The science

IGF-1 LR3 adds a 13-amino-acid N-terminal extension and an Arg-for-Glu substitution at position 3 to native IGF-1. These changes dramatically reduce binding to IGF-binding proteins (~1,000-fold), leaving a much larger free, bioactive fraction and extending functional half-life to ~20-30 hours; it is roughly 2-3 times more potent than native IGF-1 in models. This work was characterized in animal and in vitro studies (King et al., 1992; Tomas et al., 1993). There are no published human clinical trials of IGF-1 LR3 as a therapeutic—human clinical evidence is absent. Activating IGF-1 receptors systemically raises legitimate concerns about hypoglycemia and mitogenic/oncologic risk; it is not FDA-approved and is sold as a research chemical.

References

• King R et al., J Mol Endocrinol 1992
• Tomas FM et al., J Endocrinol 1993