GnRH Agonists

GnRH is a hormone secreted from the hypothalamus of the brain.  Synthetic GnRHa can suppress follicle maturation and maintain immature eggs in an inactive state.  It is known that actively growing eggs or mature eggs are more susceptible to chemotherapy.  Therefore, GnRH agonists can protect immature eggs from chemotherapy. There are several possible mechanisms that can explain the protective effects of GnRH agonists, which include:

1. preventing follicular growth by suppressing gonadotropin (hormone stimulating follicle growth) secretion,
2. decreasing the exposure to chemotherapeutic agents by reducing blood supply to the ovary,
3. direct effects of GnRHa independent of the suppression of gonadotropin levels. 

GnRH analogs are not indicated for patients who undergo radiation therapy.  There is no role for GnRH analogs for male cancer patients.