4-Hydroxyestradiol
4-Hydroxyestradiol (4-Hydroxy-17β-estradiol) is an endogenous metabolite of Estradiol (HY-B0141). 4-Hydroxyestradiol is carcinogenic and shows mutagenic activity in breast epithelial cells. 4-Hydroxyestradiol inhibits the binding of Estradiol to the estrogen receptor in a competitive manner, with a Ki of 0.48 nM.