Steroid hormone receptors

Steroid hormone receptors are target sites for several important drugs.

Tamoxifen binds to estrogen receptors but does not activate estrogen-responsive genes.

The growth of some breast tumor cells is activated by estrogen. Tamoxifen treatment of patients with such tumors after surgery or chemotherapy often antagonizes estrogen binding in residual tumor cells and retards their growth.

RU486, binds to progesterone receptors and blocks the events essential to implantation of a fertilized ovum in the uterus. Hence, RU486 is an effective contraceptive agent, even when taken after intercourse.