Furthermore, consistent with the 3- to 4-fold prevalence of both benign and malignant thyroid tumors in females compared to males, both ER isoforms have been detected in goiter tissues and TC, and it has been hypothesized that changes in the ERα:ERβ subtype ratio expression may enhance cell proliferation (ERα dominance) or induce cell apoptosis and tumor suppression in PTC (ERβ dominance) [165,166]. This evidence concerns the gene ESR1 and thyroid cancer.