Sterility, permanent inability to produce offspring. Sterility can be caused by improper functioning of the sex organs, which in humans are the testes in the male and the ovaries in the female. Such malfunctioning may be the result of a disease or an injury affecting the organs, or it may be due to abnormal development of the organs. Sterility can also be caused by the abnormal release of hormones that control the activities of the sex organs (see Sex Hormone). Sometimes it results from surgical removal of the ovaries (see Hysterectomy) or testes in order to treat a serious disorder such as cancer. In many cases, failure to reproduce is caused not by sterility but by disorders that cause infertility. These disorders include low sperm count in the male or obstruction of the fallopian tubes (tubes that carry the egg from the ovary to the uterus) in the female, either of which makes conception (fertilization of the egg by a sperm) difficult. Infertility disorders can often be corrected through procedures such as artificial insemination, in vitro fertilization, or fertility drugs to increase production of healthy sperm and eggs.