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.
Estrogen (medication)
Testosterone, prasterone (dehydroepiandrosterone; DHEA), boldenone (δ-testosterone), and nandrolone (19-nortestosterone) are naturally occurring androgens/anabolic steroids (AAS) which form estradiol as an active metabolite in small amounts and can produce estrogenic effects, most notably gynecomastia in men at sufficiently high dosages. Similarly, a number of synthetic AAS, including methyltestosterone, metandienone, normethandrone, and norethandrolone, produce methylestradiol or ethylestradiol as an active metabolite in small quantities, and can produce estrogenic effects as well. A few progestins, specifically the 19-nortestosterone derivatives norethisterone, noretynodrel, and tibolone, metabolize into estrogens (e.g., ethinylestradiol) and can produce estrogenic effects as well.