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Antigonadotropins are drugs which exert negative feedback on the hypothalamic-pituitary-gonadal (HPG) axis and thereby inhibit the secretion of gonadotropins from the pituitary gland, which in turn suppresses production of sex hormones by the gonads and hence can lower blood levels of testosterone, estradiol, and progesterone. Antigonadotropins include estrogens, progestogens, and androgens/anabolic steroids, as well as GnRH agonists and antagonists. They are functional antiandrogens by suppressing testosterone production in AMABs; GnRH agonists/antagonists and sufficiently high doses of estrogens can reduce testosterone levels by up to 95% in AMABs, whereas sufficiently high doses of progestogens can reduce testosterone levels by up to 70 to 80% in AMABs. Similarly, testosterone treatment at sufficiently high doses substantially suppresses estradiol and progesterone levels in AFABs.
The opposite of antigonadotropins are progonadotropins, which increase the secretion of gonadotropins from the pituitary gland and activate gonadal sex hormone production. Examples include antiestrogens like SERMs (e.g., tamoxifen, raloxifene) and aromatase inhibitors (e.g., anastrozole), and antiandrogens like pure androgen receptor antagonists (e.g., bicalutamide, enzalutamide).