Men with a genetic variant on the Y chromosome are NINE times more likely to have fertility issues, study warns
- Male infertility is estimated to affect around 10 per cent of men in the UK
- But the cause for roughly 60 per cent of these men remains unclear
- Scientists studied genomes of 2,300 men in Estonia, half who had fertility issues
- Some of the men carried a genetic variant on the Y chromosome, affecting the region known to be important for the development of sperm cells
- Monitoring for the genetic variant could help to identify men at higher risk early
It’s an issue that affects around 10 per cent of men in the UK, yet the cause of roughly 60 per cent of cases of male infertility remains unknown.
Now, scientists have discovered a genetic variant on the Y chromosome that significantly increases the risk of infertility issues in men.
The variant appears to affect the region of the Y chromosome that is important for the development of sperm cells.
The researchers hope that monitoring for the genetic variant could help to identify men at higher risk in their early adulthood, allowing them to make more informed decisions around future family planning.
Scientists have discovered a genetic variant on the Y chromosome that significantly increases the risk of infertility issues in men (stock image)
The Y chromosome
Human body cells have 23 pairs of chromosomes in the nucleus.
Twenty two pairs control most of the characteristics, while pair 23 are the sex chromosomes.
They carry genes that determine an embryo’s sex – whether offspring are male or female.
– Males have two different sex chromosomes, XY
– Females have two X chromosomes, XX
In the study, researchers from the Wellcome Sanger Institute and University of Tartu carried out the largest genetic study to date looking at unexplained infertility in men.
More than 2,300 men from Estonia were recruited for those study – around half of who were experiencing unexplained fertility problems.
An analysis of their genomes revealed that some of these men carried a genetic variant on the Y chromosome, with an inversion in the region known to be important for the development of sperm cells (spermatogenesis).
While the inversion itself does not appear to have a direct effect on fertility, it leads to the carrier having a higher chance of genetic deletion of this part of the Y chromosome.
A deletion can increase the risk of a low, or even non-existent sperm count nine-fold, according to the researchers.
The inversion alone is relatively common and can be passed on from father to son, and is found in a ‘significant number’ of men of European descent.
Dr Pille Hallast, co-author and Senior Staff Scientist at the University of Tartu and the Wellcome Sanger Institute, said: ‘Our study is the largest, most sophisticated look at the genetic variation of this particular Y-chromosomal region that can increase the risk of impaired sperm production in men.
The researchers hope that monitoring for the genetic variant could help to identify men at higher risk in their early adulthood, allowing them to make more informed decisions around future family planning (stock image)
‘By having access to such a large number of patients and reference men, and being able to compare their genetic data to andrological information, we identified a common Y-chromosome subtype that is susceptible to genetic changes leading to low sperm count, but also can go unnoticed and passed down in families until a deletion in this genomic region occurs.’
The team hopes their findings could lead to screening for this subtype, inversion and deletion to help men understand the root cause of any fertility issues.
Professor Maris Laan, senior co-author and Professor of Human Genetics at the Institute of Biomedicine and Translational Medicine, University of Tartu, Estonia, said: ‘Being able to identify the genetic reason for these men having impaired sperm production will help give them a diagnosis and access to the support that this brings.
‘While some deletions on the Y chromosome were previously known to interfere with sperm production, understanding at this level of detail is important for the management of male fertility issues, and in this case the options of having children early in life or preserving sperm for later use could be discussed.’
In the UK, it is estimated that infertility affects up to one in seven heterosexual couples.
The NHS explained: ‘There are many possible causes of infertility, and fertility problems can affect either partner. But in a quarter of cases it is not possible to identify the cause.’
THE CAUSES OF MALE INFERTILITY
The most common cause of infertility in men is poor-quality semen, the fluid containing sperm that’s ejaculated during sex.
Possible reasons for abnormal semen include:
- a lack of sperm – you may have a very low sperm count or no sperm at all
- sperm that aren’t moving properly – this will make it harder for sperm to swim to the egg
- abnormal sperm – sperm can sometimes be an abnormal shape, making it harder for them to move and fertilise an egg
Many cases of abnormal semen are unexplained.
There’s a link between increased temperature of the scrotum and reduced semen quality, but it’s uncertain whether wearing loose-fitting underwear improves fertility.
The testicles produce and store sperm. If they’re damaged, it can seriously affect the quality of your semen.
This can happen as a result of:
- an infection of your testicles
- testicular cancer
- testicular surgery
- a problem with your testicles you were born with (a congenital defect)
- when one or both testicles hasn’t descended into the scrotum, the loose sac of skin that contains your testicles (undescended testicles)
- injury to your testicles
Some men choose to have a vasectomy if they don’t want children or any more children.
It involves cutting and sealing off the tubes that carry sperm out of your testicles (the vas deferens) so your semen will no longer contain any sperm.
A vasectomy can be reversed, but reversals aren’t usually successful.
Hypogonadism is an abnormally low level of testosterone, the male sex hormone involved in making sperm.
It could be caused by a tumour, taking illegal drugs, or Klinefelter syndrome, a rare syndrome where a man is born with an extra female chromosome.
Medicines and drugs
Certain types of medicines can sometimes cause infertility problems.
These medicines are listed below:
- sulfasalazine – an anti-inflammatory medicine used to treat conditions such as Crohn’s disease and rheumatoid arthritis; sulfasalazine can decrease the number of sperm, but its effects are temporary and your sperm count should return to normal when you stop taking it
- anabolic steroids – are often used illegally to build muscle and improve athletic performance; long-term abuse of anabolic steroids can reduce sperm count and sperm mobility
- chemotherapy – medicines used in chemotherapy can sometimes severely reduce sperm production
- herbal remedies – some herbal remedies, such as root extracts of the Chinese herb Tripterygium wilfordii, can affect the production of sperm or reduce the size of your testicles
- illegal drugs, such as marijuana and cocaine, can also affect semen quality.