Therefore, our study was designed to 1) determine the relationship between testicular volume, levels of reproductive hormones (follicle-stimulating hormone – FSH, luteinizing hormone – LH, prolactin – PRL, total testosterone – total T, thyroid-stimulating hormone – TSH), standard semen analysis and sperm genomic integrity and 2) compare standard semen parameters and investigated biomarkers of male infertility between groups of participants with low, moderate and high levels of nuclear DNA fragmentation. The gene discussed is PRL; the disease is male infertility.