GnRH agonists/antagonists

GnRH agonists/antagonists lower testosterone in people with testicles, and lower estrogen in those with ovaries. Since they both achieve the same results, they have similar uses, such as for treating hormone related conditions such as breast and prostate cancer, fibrocystic breasts, endometriosis, and polycystic ovarian disease (PCOS).

Both kinds of compounds work by stopping the production of GnRH hormone by the pituitary gland (though they have different methods of action), which tell the ovaries or testes to produce estrogen or testosterone.

Agonists overstimulate production of GnRH, which can lead to hormone spikes at first, but then lead to less hormones being produced as the pituitary gland stops making GnRH.

Antagonists compete with and replace GnRH, but don’t act as it, effectively halting GnRH production. They have no hormone surge as with agonists.

Agonists are medications such as Lupron (leuprolide acetate) and Zoladex (goserelin acetate). Lupron is already used as a hormone blocker to suppress puberty, and is used in endometriosis treatment.

Antagonists include medications like and Buserelin. Both are often used for treatment of fibrocystic breasts and endometriosis, and cancers such as breast cancer and prostate cancer. Lupron is already used as a “puberty blocker” in transgender people, and Buserelin is sometimes used in breast cancer treatment is conjunction with other medicines like tamoxifen.

Both kinds of GnRH suppressors may be used to reduce levels of unwanted hormones produced by the body, and subsequently agonists could be used with a combination of hormones, like estrogen+a SERM (tamoxifen/ralixofen), testosterone and finasteride, etc.