KLK3 and benign prostatic hyperplasia: Furthermore, in a multicenter study evaluating the relationship between serum prostate-specific antigen and prostate volume, Chung et al. [23] obtained similar findings regarding PSA levels by age decade (PSA levels of >1.3 ng/mL, >1.7 ng/mL, and >2.0 ng/mL for men with BPH in their sixth, seventh, and eighth decades, respectively).