Hormoneblocking

Hormoneblocking is a broad term for strategies that reduce or block the actions of hormones by interfering with production, release, receptor binding, or signaling. It is used in medicine to treat conditions driven by hormonal signaling and in research to study endocrine systems. It is distinct from hormone replacement, which aims to raise hormone levels.

Major mechanisms include receptor antagonism, where a compound binds a hormone receptor without activating it (for example, anti-estrogens such as fulvestrant and the selective estrogen receptor modulators, and anti-androgens such as bicalutamide and enzalutamide). Inhibition of hormone synthesis, as with aromatase inhibitors (anastrozole, letrozole) that reduce estrogen production, or thyroid synthesis inhibitors (methimazole, propylthiouracil). Downregulation of hormone-producing pathways can be achieved with GnRH receptor antagonists (degarelix) or GnRH agonists (leuprolide) that suppress gonadotropin release.

Applications include treatment of hormone-sensitive cancers, contraception, and management of endocrine disorders such as hyperthyroidism or endometriosis. Examples span tamoxifen, fulvestrant, aromatase inhibitors, antiandrogens, GnRH analogs, methimazole, 5-alpha-reductase inhibitors (finasteride), and progesterone receptor antagonists like mifepristone.

Side effects and risks depend on the mechanism and context, including hot flashes, osteoporosis, fatigue, and metabolic changes. Resistance can occur in some diseases, and therapy is guided by clinical guidelines and individual risk–benefit assessments.