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Causes of male infertility
Male infertility can have a number of different causes with one or more reasons being present in any individual man. Some of these causes can affect several different processes at the same time. The causes of male infertility have been classified by many doctors in the following way:
Pre-testicular causes affect the hormones which control testicle function, meaning the hormone signalling is faulty or defective in some way. This means the testicles don’t get the proper signals to produce sperm, even though they might be healthy. The hormones involved are generally released from control centres in the brain such as the hypothalamus or pituitary gland.
Testicular causes stop the testicles from working properly either because of disease, damage or incorrect development. An example is a reduction in the number of sperm-producing cells in the testicles because of cancer treatment. Also testicles work best at 33°C and if they get too hot they will not be able to produce as many sperm.
Post-testicular causes affect the release or delivery of sperm at ejaculation. They include issues with erectile dysfunction or blockages in the tiny tubes that sperm have to travel through which can be related to infection or inflammation.
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Diagnosis of male infertility
Regardless of the exact cause or causes of male infertility, most are associated with either a change in the levels of key hormones in blood or the lack of adequate numbers of swimming sperm in a man’s ejaculate.
If a man suspects he has a fertility problem, then a doctor would usually begin the process of diagnosis by asking about his medical and sexual history before performing a physical examination of his genitals. A physical examination is performed to check that the testicles are properly developed and in the correct place. Sometimes a doctor will assess the size of a man’s testicles by comparing them to a string of calibrated beads as shown below:
This is very useful because the volume of a man’s testicles is directly correlated to the number of sperm he is able to produce at any one time. The testicular volume of an average man is about 15 millilitres (which is a bit less fluid than an imperial tablespoon can hold).
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The next stage in the diagnostic pathway is to invite the man to a laboratory specialised in andrology to provide a sample of semen for analysis. There are well established international guidelines which describe how to perform a semen analysis and these are summarised below:
- The man must abstain from ejaculation for between 2 and 7 days before producing his semen sample. This allows us to get an accurate picture of how many sperm are produced and stored by his body over this time period.
- The semen sample must be delivered within one hour of production so that it can be examined quickly before the sperm have died. During this time it is recommended that the semen sample is kept at (or close to) body temperature (37oC).
- In the laboratory, the volume, appearance and acidity (pH) of the sample is recorded first before three small samples are removed to give a measurement of:
• Sperm concentration (how many sperm are present in each millilitre of semen).
• Sperm motility (how many sperm are swimming and how fast they are moving).
• Sperm morphology (how many sperm have the correct size and shape).
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Measurement of sperm motility
This section of the website will explain in more detail how sperm motility is assessed, as this project is concerned with the production of energy molecules required to make sperm swim.
In most situations, sperm motility is assessed by a trained scientist who observes 200 sperm and classifies each one into one of three groups:
Progressive motility (PR) sperm are actively moving and either swimming in a straight line or in a large circle;
Non-progressive motility (NP) sperm are those swimming in any other pattern but are not moving forward. For example, they could be swimming in small circles or just shaking on the spot;
Immotile (IM) sperm are those which are not moving. These sperm could be dead, structurally abnormal or simply do not metabolise correctly .
Take a look at the video below and see if you can identify these three types of sperm in the sample.
Computers aided sperm analysis (CASA) can also be used to identify sperm.
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Treatment of male infertility
Unfortunately, there are relatively few treatments for male infertility. In most cases, doctors are unable to give any drugs to increase the number of sperm a man produces. Similarly, there are no ways to stimulate sperm to swim or to improve their size and shape. Therefore, for men who have infertility because of poor sperm, there are only three techniques to help them father a child:
Intra-uterine Insemination (IUI): This is where the best sperm are recovered from a man’s ejaculate and are washed in the laboratory before being inseminated into his partner a few hours before ovulation takes place. For it to work, the sperm must still make their own way to the egg and fertilise it inside the women’s body.
In vitro fertilisation (IVF): This is where eggs and sperm are incubated together in a laboratory dish for 24 hours. In this environment, sperm still have to find and fertilise an egg (although they don’t have as far to swim)
Intra-cytoplasmic sperm injection (ICSI): This is a where a single sperm is injected directly into each egg using a fine needle. In this case, sperm do not need to be able to swim at all. But the DNA inside the sperm head does need to be in good condition so that it can combine with the woman’s DNA and produce an embryo.
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