Accordingly, the increased risk of breast cancer in postmenopausal women who gain large amounts of weight or are overweight is attributed to excess plasma levels of oestrogens, together with low levels of sex-hormone-binding globulin (SHBG) (Stoll, 1994; Thomas et al, 1997; Endogenous Hormones and Breast Cancer Collaborative Group, 2003; Calle and Kaaks, 2004). Here, SHBG is linked to breast cancer.