IGF1 and benign prostatic hyperplasia: In addition to 5α-reductase, estrogen and androgen, and their receptor-related genes, BPH is associated with the elevated expression of many genes, which mainly include growth factors; BPH has been found to be associated with abnormal expression of growth factors such as FGF [25], TGF-β [26], EGF [27], and IGF [28].