4-Hydroxyestradiol is a catechol estrogen and minor metabolite of estrogen.[1][2] 4-Hydroxyestradiol is formed from estrogen by the cytochrome P450 (CYP) isoform CYP1B1.[2] Production of 4-hydroxyestradiol is increased in microsomes prepared from human mammary adenocarcinoma and fibroadenoma microsomes compared with microsomes prepared from non-cancerous tissues.[1] 4-Hydroxyestradiol (25 mg/animal) induces renal tumor formation in male hamsters.[3]
Reference:
[1]. Liehr, J.C., and Ricci, M.J. 4-Hydroxylation of estrogens as marker of human mammary tumors. Proc. Natl. Acad. Sci. USA 93(8), 3294-3296 (1996).
[2]. Yager, J.D., and Liehr, J.G. Molecular mechanisms of estrogen carcinogenesis. Annu. Rev. Pharmacol. Toxicol. 36, 203-232 (1996).
[3]. Liehr, J.G., Fang, W.F., Sirbasku, D.A., et al. Carcinogenicity of catechol estrogens in Syrian hamsters. J. Steroid Biochem. 24(1), 353-356 (1986).