RT-qPCR and Western blot analysis revealed down-regulation of ERα mRNA (p < 0.05; Figure 1B) and protein (p < 0.05; Figure 1E) expression in human and mouse endometriosis tissues, and up-regulation of ERβ mRNA (p < 0.05; Figure 1C) and protein (p < 0.05; Figure 1E) expression relative to normal human and mouse intimal tissues, thereby giving an increased ratio of ERβ/ERα mRNA (p < 0.05; Figure 1D) and protein expression (p < 0.05; Figure 1F). Here, ESR1 is linked to endometriosis.