On Jun. 17, 2020, DNA from uterine cells of women with endometriosis has different chemical modifications, compared to the DNA of women who do not have the condition, according to researchers funded by the NIH. The changes involve DNA methylation ﾗ the binding of compounds known as methyl groups to DNA ﾗ which can alter gene activity. Moreover, the methylated DNA regions varied according to the stage, or severity, of endometriosis and responded differently to hormones involved in the menstrual cycle. Uterine responses to hormones influence pregnancy and other functions of uterine tissue.