Sexually transmitted diseases can also cause infertility in men. Similar to how PID damages a woman's fallopian tubes, the structures of the male reproductive tract, including the epididymis and urethra, can be compromised by infection with an untreated STDs. Immunodeficiency from HIV can also reduce semen quality in men and impair their ability to impregnate their partners. STD-related infertility is less common in men than in women, but that is partially due to the fact that STD infections in men are more likely to cause symptoms and thus more likely to be treated.
The problem of unnoticed and untreated STDs causing extensive damage over time is one reason why STD screening is so important. Regular STD screening helps catch asymptomatic infections that might otherwise go unnoticed, and untreated, for years. Not only is this important in slowing the spread of the STD epidemic, it also can help preserve a person's ability to have children.
Ochsendorf FR (2008)"Sexually transmitted infections: impact on male fertility." Andrologia. 2008 Apr;40(2):72-5.