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GnRH analogs (agonists and antagonists)

GnRH (also called LHRH) analogs act on the pituitary gland to shut down sex-hormone production — testosterone in men and estrogen in premenopausal women. Agonists (leuprolide, goserelin, triptorelin), given as injections or implants, suppress hormone production after an initial, temporary rise, while antagonists block it right away, without that flare — degarelix is injected, and relugolix is taken as a daily tablet. They form the backbone of androgen deprivation in prostate cancer and provide reversible ovarian suppression in premenopausal women with breast cancer.

How it works

The pituitary gland controls the testicles and ovaries: in response to the hormone GnRH it releases signals that tell them to produce testosterone or estrogen. GnRH agonists at first overstimulate the pituitary — in men this can cause a temporary "testosterone flare" that may briefly worsen symptoms such as bone pain — but with continued exposure the pituitary stops responding, the signal disappears, and the testicles or ovaries cease hormone production. This state, known as medical castration or ovarian suppression, is reversible after the drug is stopped. GnRH antagonists work differently: they immediately block the receptors in the pituitary, so hormone levels fall quickly and no initial flare occurs.

Used in

Invasive Breast Carcinoma C50

Ovarian function suppression in premenopausal women with hormone-receptor-positive disease, combined with tamoxifen or an aromatase inhibitor; a separate use is ovarian protection during chemotherapy.

Prostate C61

Backbone of androgen deprivation: agonists (goserelin, leuprolide) and antagonists (degarelix, relugolix); meta-analyses show no outcome difference versus orchiectomy.

Sources

  1. NCI – Hormone Therapy for Prostate Cancer ↗
  2. NCI – Hormone Therapy for Breast Cancer ↗