Insulin-like growth factor-1 (IGF-1) levels are higher in young black woman than in young white women (Jernström et al, 2001a) and a higher level of circulating IGF-1 is a known risk factor for early-onset breast cancer (Peyrat et al, 1993; Hankinson et al, 1998; Renehan et al, 2004; Sugumar et al, 2004; Fletcher et al, 2005; Schernhammer et al, 2005). This evidence concerns the gene IGF1 and breast cancer.