In 1966, a urologist named Charles Huggins won the Nobel prize for the discovery that the prostate growth is dependent on testosterone. Testosterone is a hormone which is produced in the testicles. Eliminating testosterone from the blood stream of a prostate cancer patient will provide a period of disease remission. This castration is achieved either surgically (removal of the testes) or medically (shots). Patients can typically expect a long period of cancer control, but side effects are common (hot flashes, fatigue, impotence, osteoporosis). Hormone ablation is not a curative treatment, as the cancer eventually begins to grow without testosterone. It is most often employed for older patients, aggressive cancers, or when cancer recurs after other treatments.