Castration (also known as gonadectomy) is any action, surgical, chemical, or otherwise, by which a biological male loses use of the testicles. Surgical castration is bilateral orchiectomy (excision of both testes), and chemical castration uses pharmaceutical drugs to inactivate the testes. Castration causes sterilization (i.e., prevents them from reproducing); it also greatly reduces the production of certain hormones, such as testosterone. Surgical castration in animals is often called neutering.