Genetic polymorphism occurs within the endometrial tissue, concerning estrogen and progesterone receptors [66,67], as well as the polymorphism of the enzymes responsible for the metabolism of drugs (CYP1A1, CYP19, and GSTM1), predisposing to endometriosis [68,69,70,71]. The gene discussed is CYP19A1; the disease is endometriosis.