In a study by Choi et al. [7], the serum PSA levels in the MetS group were lower than those in the control group (1.15 ± 0.91 vs. 1.26 ± 0.76 ng/ml, P = 0.006), and after adjusting for PV and plasma volume, the results were also significantly correlated. The gene discussed is KLK3; the disease is metabolic syndrome.