Chemical castration is castration via drugs, whether to reduce libido and sexual activity, to treat cancer, or otherwise. Unlike surgical castration, where the gonads are removed through an incision in the body, chemical castration does not remove organs, nor is it a form of sterilization. Chemical castration is generally considered reversible when treatment is discontinued, although permanent effects in body chemistry can sometimes be seen, as in the case of bone density loss increasing with length of use of DMPA.