PCa patients have significantly lower serum levels of 25(OH)-vitamin D [16.2 (0.3–54.1) vs. 23.2 (0.3–89.8) (ng/ml), p < 0.001] and FPSA/TPSA ratio [0.21 (0.01–2.5) vs. 0.48 (0.01–3.5), p < 0.001] and higher serum levels of free PSA [14.5 (0.1–109) vs. 0.4 (0.1–1.9) (ng/L), p < 0.001] and total PSA [76.8 (0.4–572) vs. 0.4 (0.1–1.9) (ng/L), p < 0.001] compared to control group. Here, KLK3 is linked to posterior cortical atrophy.