Androgen deprivation therapy (ADT) comes in several forms, such as surgical castration or medical castration using gonadotropin-releasing hormone (GnRH) agonist or GnRH antagonist therapy. ADT is a critical treatment for high-risk and metastatic prostate cancer. There are important differences between GnRH agonists and antagonists. Here we review the mechanism of action between GnRH agonists and antagonists and the studies that led to the approval of degarelix. We also comment on the potential risks and benefits of degarelix, particularly when it comes to cardiovascular health. Finally, we describe an oral GnRH antagonist, which is not currently used in prostate cancer, but is included for completeness.