In conjunction with the earlier onset and longer duration of pubertal maturation observed in African Americans, exposure to high levels of IGF-1 and low levels of IGFBP-3, which have been speculated to facilitate tumour invasion and metastases,39,56 during a critical window of prostate development could increase susceptibility to prostatic neoplasia, particularly of a more aggressive nature, leaving lasting, long-term effects on the prostate, and thus possibly account for the well-known racial differences in the burden of prostate cancer. Here, IGF1 is linked to prostate cancer.