IGF1 and breast cancer: These include hormones such as insulin-like-growth factor I (IGF-I) (Hankinson et al, 1998; Kaaks et al, 2002), energy intake in childhood (McCay et al, 1939; Hart and Turturro, 1997; Frankel et al, 1998), and also intrauterine growth, reflected by birth weight, which has been found to be positively associated with breast cancer risk (Michels et al, 1996; Stavola et al, 2000; Vatten et al, 2002).