Xenoestrogen
Xenoestrogens are a type of xenohormone that imitates estrogen. They can be either synthetic or natural chemical compounds. Synthetic xenoestrogens include some widely used industrial compounds, such as PCBs, BPA, and phthalates, which have estrogenic effects on a living organism even though they differ chemically from the estrogenic substances produced internally by the endocrine system of any organism. Natural xenoestrogens include phytoestrogens which are plant-derived xenoestrogens. Because the primary route of exposure to these compounds is by consumption of phytoestrogenic plants, they are sometimes called "dietary estrogens". Mycoestrogens, estrogenic substances from fungi, are another type of xenoestrogen that are also considered mycotoxins.
Cyanoketone
Cyanoketone, also known as 2α-cyano-4,4',17α-trimethylandrost-5-en-17β-ol-3-one (CTM), is a synthetic androstane steroid and a steroidogenesis inhibitor which is used in scientific research. On account of its structural similarity to pregnenolone, cyanoketone binds to and acts as a potent, selective, and irreversible inhibitor of 3β-hydroxysteroid dehydrogenase (3β-HSD), an enzyme that is responsible for the conversion of pregnenolone into progesterone, 17α-hydroxypregnenolone into 17α-hydroxyprogesterone, into androstenedione, and androstenediol into testosterone. As such, cyanoketone inhibits the production of both gonadal and adrenal steroids, including progesterone, androgens, estrogens, and corticosteroids. The drug is too toxic for therapeutic use in humans, and so has been used instead exclusively as a research tool.