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.
Transgender hormone therapy (female-to-male)
Antiestrogens (or so-called "estrogen blockers") like aromatase inhibitors (AIs) (e.g., anastrozole) or selective estrogen receptor modulators (SERMs) (e.g., tamoxifen) can be used to reduce the effects of high levels of endogenous estrogen (e.g., breast development, feminine fat distribution) in transgender men. In addition, in those who have not yet undergone or completed epiphyseal closure (which occurs during adolescence and is mediated by estrogen), antiestrogens can prevent hip widening as well as increase final height (estrogen limits height by causing the epiphyses to fuse).