In addition, immunohistochemical and quantitative RT PCR studies have also revealed that the expression level of ESR1 gene is approximately 50 fold higher compared to ESR2[33] In animal models, 17beta estradiol promoted gallstone formation involves upregulation of hepatic expression of ERalpha but not ERbeta, and the lithogenic actions of estrogen can be blocked completely by the antiestrogenic agents ICI 182,780 [34]. Here, ESR1 is linked to gallstones.