What the research shows

White and colleagues compared seven growth-restricted fetal sheep exposed to LR3 with seven controls. After one week the groups had similar body weights and insulin responses to glucose. Amino acid levels fell in the LR3 group. The experiment offers no measure of adult human muscle growth. Read the fetal sheep study.

A separate structural study used magnetic resonance to map the modified protein in solution, including its extra segment. See the solution structure.

Documented formats

The structural experiment used a nitrogen-labeled version of Long R3 IGF-1 so researchers could trace its backbone. The isotope label identifies material prepared for that measurement.

Testing and purity

Check the full sequence against the study, including the extension and substitution. An assay that reports total IGF-1 needs additional evidence to distinguish LR3 from ordinary IGF-1.

How to read a batch report

Questions about IGF-1 LR3

What does R3 mean?

R is the one-letter code for arginine. It replaces glutamic acid at the third position of the original IGF-1 sequence.

Did the sheep gain weight because of LR3?

The treated and control fetuses had similar body weights at the end of this experiment. The investigators reported the fall in circulating amino acids as a separate finding.