Most prostate cancers are hormone-dependent, so the tumor can only grow with the help of the male sex hormone testosterone. Almost all testosterone is produced in the testicles; a small amount is produced by the adrenal glands. The first step to stop prostate cancer growing is to stop the body from making testosterone. However, hormone therapy injection only stops the testicles making testosterone (see LHRH or GNRH analogues/antagonists) and hormone blocking pills stop testosterone attaching to the cancer cells (see androgen receptor blocker). If these options no longer work, we call this hormone-refractory prostate cancer (HRPC) or castration-resistant prostate cancer