Though the cause of male infertility is often unidentified, there are a few problems that have been indicated as potential causes. Problems related to sperm production, the anatomy or structure of the man's reproductive organs and the man's immune system can all be factors in male infertility.
Genetic defects, infection, testicular trauma, hormonal imbalance or exposure to radiation and certain medications are all causes of sperm production disorders. Infertility can occur when there is a low sperm count, or problems with the motility (movement) or morphology (appearance or shape) of sperm. Sperm of poor motility often is not able to reach the egg and, therefore, fertilization does not occur. Abnormal sperm is sometimes unable to penetrate and fertilize the egg. Sperm DNA damage may interfere with conception as well as lead to a greater risk of miscarriage.
Any structural or anatomical problems (bent or curved penis) that block the path that sperm must travel to eventually reach the egg for fertilization can cause male infertility. Infertility related to structural and anatomical problems in the male anatomy may be caused by scar tissue, varicose veins or infection or, in some cases, the problems exist from birth.
In some cases, men have immune system disorders which cause their bodies to develop antibodies to their own sperm, which attack and weaken the sperm. The antibodies can also attach to the sperm surface and interfere with their movement or ability to fertilize the egg.