GPX1 and Infertility: The present observational case–control study aimed to evaluate differences in the concentrations of PGE2, 6-keto-prostaglandin F1α (6-keto-PGF1α, stable metabolite of PGI2), F2-isoprostane, SOD1, GPX1, NOS1 as well as the ratios: NOS1/SOD1, NOS1/GPX1, GPX1/SOD1 and PGE2/6-keto-PGF1α in seminal plasma from fertile and infertile men, including comparisons between subgroups of infertile individuals for the purpose of evaluating the utility of the investigated parameters as biomarkers of male infertility.