2-Fluoroestradiol. Separation of estrogenicity from carcinogenicity.

Estrogenic and carcinogenic activity are shown to be separable properties. 2-Fluoroestradiol, a modified estrogen, did not induce renal clear-cell carcinoma in male Syrian hamsters despite its estrogenic potency, which is comparable to that of estradiol. 4-Fluoroestradiol, also a potent estrogen, did induce renal clear-cell carcinoma in this animal model, but more slowly than estradiol. 2,4-Dideuterioestradiol was found to be as estrogenic and also as carcinogenic as estradiol itself.