Although Tang et al. (2007[10]) showed that there was little difference in AR expression between the peripheral zone and TZ hyperplastic nodules, there was a recent study that showed that the periurethral area of the TZ (site of the primary BPH nodule), exhibited the highest levels of both androgens and AR compared with other regions; this suggested that this region may be responsible for the growth-promoting processes inherent to BPH that can result in urinary obstruction (Monti et al., 1998[9]). This evidence concerns the gene AR and benign prostatic hyperplasia.