KLK3 and benign prostatic hyperplasia: These results and the fact that BPH is known25 to increase serum PSA levels, prompted us to check the association of all 23 BPH/LUTS variants with serum levels of PSA in a sample set of 33,572 Icelandic males, not known to have been diagnosed with prostate cancer or symptomatic BPH/LUTS.