IGF-1 is found in nearly all cells of the body. What is IGF-1? It is a chain of 70 amino acids that aid in cell rejuvenation and growth. IGF-1 is short for Insulin-like Growth Factor. Structurally it is very close to insulin and interacts similarly. Of its many functions, IGF-1 is most known for its involvement in growth spurts, helping children reach their physical and developmental potential.*
The work of IGF-1 doesn’t stop at the growth spurt, it continues to have a role in many of the body’s processes throughout your life. It helps with brain health , bone density, cell rejuvnation, muscle strength , and a various other youth promoting functions.*
With all the purported benefits of IGF-1, numerous scientific studies have been conducted with more in progress. Some of these include studies about the correlation between IGF-1 and muscle strength, longer lifespan, and nerve health .*
Did you ever think that lifespan is simply a result of the daily stresses and other larger health related events in your life? Researchers have found that is also has to do with the levels IGF-1 in your body and its pathways.
Scientists studied the effect of IGF-1 on a variety of life forms including yeasts, worms, flies, and mice. They found a direct correlation between the levels of IGF-1 and lifespan. With such results across these evolutionary organisms, the authors of these tests are quite hopeful about the effects IGF-1 can have on humans. They also studied centurions (those who live past 100 years) as well as those in their families. You know what they found? The centurions and their offspring from the study all had much higher serum levels of IGF-1 than the control group did (which consisted of healthy people, similar to those in the study but without extreme longevity in their family lines).
On the other hand, people born with, or who somehow develop defects in their Insulin/IGF-1 pathway are at a far higher risk of age-related disease and even shorter lives. To achieve the greatest longevity and health, fully functioning IGF-1/Insulin pathways are vital.* 
Derek LeRoith. Minireview: Insulin-Like Growth Factors and the Brain Endocrinology 2008 149(12):5951; doi: 10.1210/en.2008-1190.
Gabriella Dobrowolny, Cristina Giacinti, Laura Pelosi, Carmine Nicoletti, Nadine Winn, Laura Barberi, Mario Molinaro, Nadia Rosenthal, and Antonio Musarò. Muscle expression of a local Igf-1 isoform protects motor neurons in an ALS mouse model. Journal of Cell Biology 2005 vol. 168 no. 2 193-199 doi: 10.1083/jcb.200407021
Kelli A. Sullivan, Bhumsoo Kim and Eva L. Feldman. Insulin-Like Growth Factors in the Peripheral Nervous System Endocrinology 2008 149: 5963-5971; doi:10.1210/en.2008-1020