ESR1 and inflammatory bowel disease: Estrogen receptors are expressed in various types of colon tissue cells [19] as well as in circulating monocytes [29] Both major ER isoforms have been linked with IBD, as recent studies suggest that ERα expression increases and ERβ decreases with IBD activity, and thus, increasing ERα/ERβ ratio is characteristic for inflamed colon tissue [19,37,38].