A temporary or permanent deficiency in the number of sperm in the semen. Oligospermia is a major cause of infertility, especially when other disorders of the sperm are also present. Normally, there are more than 20 million sperm per millilitre of semen. A low sperm count can be due to various disorders, including orchitis, undescended testis (see testis, undescended), and, infrequently, a varicocele (varicose vein of the testis). Smoking, alcohol abuse, stress, and some drugs may cause temporary oligospermia. Treatment is for the underlying cause. If the cause is unknown, gonadotrophin hormones may be prescribed. (See also azoospermia.)


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