16alpha-hydroxyestrone is a naturally occurring estrone metabolite. It exerts estrogenic properties through covalent estrogen receptor (ER) binding. 16alpha-hydroxyestrone is a potential tumor initiator. The ratio 2-hydroxyestrone to 16alpha-hydroxyestrone could serve as an innovative intermediate biomarker for breast cancer risk. This biomarker could be used to identify women at high risk, and provide the analytic framework for the development of new pharmaceutical and dietary intervention strategies.

6α-Hydroxyestradiol is one of major metabolites of endogenous estrogens, as well as a positional isomer of estriol. Transformation of estradiol to 6α-Hydroxyestradiol is a major metabolic pathway of estradiol in the liver. CYP1A2 and CYP3A4 are the major enzymes catalyzing the 6α-Hydroxyestradiol of estradiol.

Estramustine is an antineoplastic agent indicated in the palliative treatment of patients with metastatic and/or progressive carcinoma of the prostate. Estramustine is a combination of estradiol with nitrogen mustard. In vivo, the nitrogen-mustard moiety becomes active and participates in alkylation of DNA or other cellular components. This causes DNA damage in rapidly dividing cancerous cells leading to cell death and ideally, tumor shrinkage. Also, due to the drugs estrogen component, it can bind more selectively to active estrogen receptors. Used for the palliative treatment of patients with metastatic and/or progressive carcinoma of the prostate.