Xenoestrogen
Xenoestrogens are clinically significant because they can mimic the effects of endogenous estrogen and thus have been implicated in precocious puberty and other disorders of the reproductive system.
Antiestrogen
Antiestrogens are mainly used as a means of estrogen deprivation therapy in the treatment of ER-positive breast cancer. They are also used to treat infertility, male hypogonadism, and gynecomastia (breast development in men) and are used as a component of hormone replacement therapy for transgender men.