The purpose of this study is to determine if patients initiating androgen deprivation therapy (ADT) for prostate cancer can be transitioned from degarelix acetate to leuprolide acetate after an initial three-month period without a rise in serum testosterone. The investigators expect testosterone will quickly and reliably reach castrate levels after initiation of ADT and will remain castrate during the transition, and there will be no "testosterone surge" after leuprolide injection.