For the purpose of conducting cluster analysis, three parameters, namely IL-6, PRL and CA 125, were selected from the panel of parameters examined, taking into account that their concentration values had to simultaneously meet the following criteria: they correlate with each other, differentiate the endometriosis group from the control group of healthy women, and have moderate or high clinical value according to the results of the ROC analysis (AUC ≥ 0.784). The gene discussed is PRL; the disease is endometriosis.