In 50 percent of infertile couples, both partners are affected because of some physical reason. In the remaining 50 percent, half the men and half the women are physically incapacitated. Therefore, a true infertility evaluation requires examination of both partners. Apart from sexual problems, infertility results if a condition or disorder affects either the total number of sperm produced during ejaculation or the number of viable, or normal, sperm produced. The temperature of the testicles affects the production of sperm.
Undescended testicles are too warm to produce healthy sperm.
In the same way, some men become temporarily infertile in hot environments or from wearing tight undershorts that hold the testicles too close to the body. More rarely, varicose veins of the spermatic cord, known as varicoceles, may cause lowered sperm counts. Other causes of infertility include certain chromosome abnormalities, Klinefelter's syndrome, cystic fibrosis, certain drugs, and irradiation of the testicles. A physician examines the man's testicles and then the prostate gland during a rectal examination. A sample of semen is collected and examined within two hours using a microscope to determine the sperm count.