There was some evidence of interactions in the associations of IGF-II, IGFBP-1 and IGFBP-2 concentrations with prostate cancer risk by total testosterone concentrations; men with total testosterone concentrations above the study-specific median showed evidence of a positive relationship for IGF-II and an inverse association for IGFBP-1, whereas these associations were null for men with lower total testosterone concentrations (Phet = 0.03 and 0.02, respectively) (Supplementary Table S9). This evidence concerns the gene IGFBP1 and prostate cancer.