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.
Ethinylestradiol
EE is an estrogen similarly to natural estrogens like estradiol and conjugated estrogens (Premarin) and synthetic estrogens like diethylstilbestrol. It binds to and activates both isoforms of the estrogen receptor, ERα and ERβ. In one study, EE was found to have 233% and 38% of the affinity of estradiol for the ERα and ERβ, respectively. In another study, it was found to possess 194% and 151% of the affinity of estradiol for the ERα and ERβ, respectively. EE also appears to signal through the GPER, a membrane estrogen receptor, similarly to estradiol. Estrogens have antigonadotropic effects through activation of the ERα. As a contraceptive, EE acts in concert with a progestin to inhibit the mid-cycle surge in luteinizing hormone (LH) and follicle-stimulating hormone (FSH) via its antigonadotropic effects, thereby inhibiting folliculogenesis and preventing ovulation and hence the possibility of pregnancy.