There are two main reasons for a low or zero sperm count. The first is that the sperm are not being made in the testes (non-obstructive), which can be a hormonal issue. The second is where a blockage prevents the sperm from reaching the ejaculate (obstructive).
It is important that men with absent or low sperm numbers are thoroughly investigated to ensure that they do not have an underlying illness or a genetic condition causing their infertility. For example, some men are carriers of the cystic fibrosis gene and may be unaware as they do not have any symptoms of the condition, however this can mean they have been born without a vas deferens.
If a genetic issue is identified then the couple can be counselled about the chances of passing a genetic problem onto their offspring, and also about the chances of success if surgical sperm retrieval is required.
Non-obstructive causes of male infertility
The manufacture of sperm can be affected by a number of problems, including:
- Genetic conditions, such as Y chromosome microdeletion or Kleinfelters syndrome, may cause an absence or very reduced number of sperm in the ejaculate.
- Testicular problems, such as undescended testicles or a previous twisted testicle, may render the testicle unable to produce sperm.
- Toxins – some drugs including steroids, used in weight training and chemotherapy, may damage the testicles’ ability to manufacture sperm.
- Previous illness, such as measles, may impair sperm production by the testicles.
- A hormonal problem (hypogonadotrophic or hypogonadism) can lead to insufficient hormones being available to support sperm manufacture.
Obstructive causes of male infertility
There are many reasons why the tubes that transport the sperm can become blocked, including: sports injuries; infections such as mumps, chlamydia or gonorrhoea; birth defects; or a previous vasectomy or failed vasectomy reversal.
Another common problem is a varicocele, which is a collection of dilated veins surrounding the testicle. The veins may be visible standing and may cause discomfort or aching.
The link between varicocele and fertility is much debated. Although varicoceles are present in 30 to 40 per cent of men with infertility, many men with the condition are able to conceive without problems. Correction of the varicocele may lead to improvement in sperm number and quality, so it is recommended that a significant varicocele should be treated to try and improve sperm quality.