Allen NE, Davey GK, Key TJ, Zhang S, Narod SA. Serum insulin-like growth factor I (IGF-I) concentration in men is not associated with the cytosine-adenosine repeat polymorphism of the IGF-I gene. Cancer Epidemiol Biomarkers Prev. 2002; 11(3):319-320.
Insulin-like growth factor-I (IGF-I) is a polypeptide involved in the control of cell growth. Several studies have found that people who have relatively high circulating levels of IGF-I are at an increased risk of developing several common types of cancer, such as breast, prostate and colorectal cancer. IGF-1 levels vary substantially between individuals and little is known about its determinants, although it is thought that part of the variation is due to genetic factors. The aim of this study was to investigate whether a common genetic mutation identified in the gene that encodes for the IGF-I protein is associated with serum IGF-I levels. We found that this particular mutation was not associated with IGF-I levels in British men, suggesting that other, as yet unidentified, genetic mutations may be more important determinants of circulating IGF-I levels and possibly subsequent cancer risk.