A recent study from our research team demonstrated that serum PSA levels in the MetS group were lower than those in the non-MetS group (1.11 ± 0.79 vs. 1.21 ± 0.76 ng/ml, P = 0.026) and that MetS was an independent risk factor for a decrease in serum PSA levels, which can reduce the serum PSA level by 11.3%. The gene discussed is KLK3; the disease is metabolic syndrome.