High levels of PSA are a useful marker for PCa detection4, for monitoring follow-up and progression after radical prostatectomy5, and for monitoring local or systemic therapy6,7, However, levels of PSA are also increased in some patients with benign prostatic hyperplasia, acute prostatitis8 or prostate manipulations, leading to unnecessary negative biopsies or to over detection of non-significant cancers. Here, KLK3 is linked to benign prostatic hyperplasia.