The video animations below depict the mechanism of action of GnRH agonists and antagonists in the treatment of prostate cancer. The three movies will start playing at the same time, you can right-click on each of them and deselect “play” in case you want to stop any of them.
This excerpt from the Wikipedia article summarizes the approach to the hormonal treatment of prostate cancer affecting the GnRH pathway:
GnRH action can be interrupted in one of two ways. GnRH antagonists suppress the production of LH directly, while GnRH agonists suppress LH through the process of downregulation after an initial stimulation effect. Abarelix is an example of a GnRH antagonist, while the GnRH agonists include leuprolide (Lupron, Eligard) , goserelin (Zoladex) , triptorelin, and buserelin(Suprefact, Suprecor) . Initially, GnRH agonists increase the production of LH. However, because the constant supply of the medication does not match the body’s natural production rhythm, production of both LH and GnRH decreases after a few weeks.
Some review papers on the role of GnRH agonists and antagonists in prostate cancer and assisted conception:
GnRH agonists in the treatment of prostate cancer. Endocrine Reviews. 2005
Gonadotrophin-releasing hormone antagonists for assisted conception. Cochrane Reviews 2001