Most (90%) circulating IGF-I is bound to IGF binding protein-3 (IGFBP-3) and associations of IGFs with prostate cancer are generally strongest with the molar ratio (IGF-I/IGFBP-3) or in statistical models controlling for IGFBP-3 (Chan et al, 1998; Harman et al, 2000; Stattin et al, 2000; Chokkalingam et al, 2001). Here, IGFBP3 is linked to Familial prostate cancer.