Causes of Male Infertility

For a man to be fertile, he has to be able to produce large quantities of functional sperm, and get them into his partner. Problems at any stage can mean infertility.

Sperm Count and Quality

For normal fertilization, a man needs to produce a very large number of sperm. Something on the order of 40 million is considered normal for one ejaculation! In most cases of male infertility, some sperm are produced, but they aren’t enough in number, or most of them are badly-formed and so unable to fertilize an egg. If your doctor uses the tongue-bending term ‘oligoasthenoteratozoospermia‘, he’s talking about this shortage of functional sperm.

Of the factors which researchers have identified as affecting the number and quality of sperm produced, many are related to lifestyle, drug use, or environmental factors. These have been discussed above, since many affect both men and women. Here, we will look at male-specific problems:


Aspermia refers to the complete failure to produce semen. It is quite rare in most cases of apparent aspermia, the semen has actually been produced, but has not been ejaculated. Retrograde ejaculation is a common example of this. True aspermia is frequently the result of genetic problems, and is typically very hard to treat.


This is a swelling of certain blood vessels in the testes. It has not been proven to cause fertility problems, but men suffering from varicocele do, on average, have lower sperm counts and poorer sperm quality. This, though, could just mean that both the varicocele and the sub fertility are symptoms of some underlying genetic problem. It has been suggested though not proved that varicocele affects fertility by changing the temperature of the testes.

The process of sperm production is highly sensitive to temperature the reason why the testicles hang outside the body is to keep them cool. If blood circulation through the testes is impaired, the body loses an important method of regulating the temperature, and it might then fail to keep the testes at that ideal, cool temperature.

Anti-sperm antibodies

The immune system is responsible for identifying and destroying harmful intruders in the body bacteria, viruses, and the like. The reproductive system is a challenge for the immune system. It needs to accept sperm as harmless, while continuing to protect the body against genuine intruders. But sperm are very different from ordinary cells for a start, they have half the number of chromosomes.

The male body gets around this problem by taking a short-cut. It doesn’t even try to teach the immune system to recognize sperm as friendly. Instead it keeps them separate: the blood-sperm barrier divides the blood (which contains immune cells) from the sperm.

If this barrier breaks down, the immune system will produce antibodies targeting the sperm. These antibodies seize hold of the sperm and cause them to be killed. Since the number of sperm produced is so high, the antibodies will not affect all of them. However, they will cause a noticeable decrease in fertility.

What can cause this damage to the blood-sperm barrier? Infection of, or physical injury to, the testes can allow blood to meet sperm. Having a vasectomy will also break the barrier. This means that even men who have a successful vasectomy reversal will have lower fertility than otherwise, since their sperm will contain anti-sperm antibodies.

More rarely, women occasionally develop anti-sperm antibodies which target their partner’s sperm.

See Also: Azoospermia