Most of thyroid diseases show female predilection, especially autoimmune thyroid diseases (AITD) and thyroid cancer (TC). We give an updated brief review here, focusing on estrogen, estrogen receptor (ER) and AITD as well as TC. Estrogen can regulate the functions of nearly all immunocyte subsets, which may contribute to the development of AITD. However, there was still lack of direct studies on ER subtype-specific effects on AITD. Recently, the local expression of ER subtypes and their individual mediated actions in the pathogenesis of TC have already received much attention. ERα activation seems to exacerbate the development of TC, while wild-type ERβ (ERβ1) plays a protective role against TC.