ESR2 and endometriosis: De novo increase of E2 in endometriosis lesions affects the ratio of Erα and Erβ, thus impacting inflammation and the expression of some target genes, such as Growth regulation by estrogen in breast cancer 1 (Greb-1) protein and multifunctional transcription factor oncogene (c-Myc), that result in endometriosis’ progression [20,21].