High levels of insulinlike growth factor (IGF)-I are associated with a modestly increased risk for prostate cancer, according to researchers.

In a study comparing 3,700 men with prostate cancer and 5,200 controls, men in the highest quintile of serum IGF-I concentration had a 38% higher risk of prostate cancer compared with those in the lowest quintile, investigators reported in Annals of Internal Medicine (2008;149:461-471).