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Understanding Klinefelter Syndrome

Klinefelter’s Syndrome is a genetic condition which occurs when a boy is born with an extra X chromosome. Men are typically born with XY chromosomes, whereas women have XX. Men with Klinefelter Syndrome have XXY chromosomes, which is why the condition is sometimes called XXY syndrome. Whilst there is so much mystery and misinformation around the condition, it actually impacts 1 in every 500 men, but the true number could be much higher, as so often symptoms go undetected until adulthood. Some men never even know they have it!

Whether you think you may have the condition or simply want to know more about it, here’s our low down on all things Klinefelter syndrome.

What causes Klinefelter syndrome?

Little is known about the cause of Klinefelter Syndrome – but really it comes down to chance. Essentially, the egg or sperm that created you had an extra X chromosome, and whilst some medical organisations believe this could be more common in older mothers, there’s still a lot more research to be done.
Are there different types of Klinefelter Syndrome? There are a few different types of Klinefelter Syndrome. You could have an extra chromosome in each cell – the most common type – or an extra X chromosome in only some cells. This is called mosaic Klinefelter, and the symptoms tend to be less noticeable. The most extreme kind of Klinefelter is when you have more than one extra X chrome – but this is very rare.

Symptoms of Klinefelter Syndrome

You might think that a condition that runs so deep is full of obvious symptoms. Many men have no idea they have it until they have issues conceiving (but more on that later).

However, there are a few symptoms that can display throughout a man’s lifetime. Some men, following a Klinefelter diagnosis, can reflect back and spot a few subtle symptoms that may have given an indication they had the condition.

Klinefelter in babies

  • Hernias
  • Not very vocal – not much crying or chatting
  • Slower development – particularly in learning to sit up, crawl, and talk
  • Weaker muscles
  • Noticeably small testicles or testicles that haven’t descended into the scrotum

Klinefelter in children

  • Low energy levels – not keen on being active
  • Problems learning to read, write, and do maths
  • Shyness and low confidence
  • Social awkwardness – finding it difficult to make friends and talk about feelings

Klinefelter in teenagers

  • Delayed puberty, or puberty never really happens
  • Less facial and body hair than other boys
  • Tall – often taller than the rest of a family
  • Longer arms and legs and shorter torsos
  • Less muscle tone and muscles grow slower than usual
  • Smaller than average penis and small, firm testicles

Klinefelter in adults

  • Low sex drive
  • Issues with erectile dysfunction
  • Low testosterone – and symptoms associated with that like tiredness and low mood
  • Infertility

What this list of symptoms misses out on is the unique and interesting ‘super powers’ that Klinefelter can also come with. Many men with the syndrome report being highly creative, emotionally intelligent and having an incredible memory! You can hear more about this in our interview with Gareth Landy.

Is there a treatment for Klinefelter Syndrome?

Whilst there is no cure for the syndrome, many symptoms can be improved with testosterone replacement therapy. This is particularly effective if the condition is spotted at a young age, as it can help encourage puberty, development of the penis and bone density. Even later in life testosterone replacement therapy can have huge benefits, especially when it comes to things like mental wellbeing, energy levels and sex drive.

Testosterone Replacement Therapy and Fertility

The one symptom that testosterone replacement therapy won’t help with is infertility. As with anything that artificially increases the amount of testosterone your body naturally produces (like steroids) testosterone replacement therapy could actually make problems with sperm production worse.
If possible, it’s best to start testosterone replacement therapy early – and try to collect and freeze some sperm ahead of time. This might not always be possible, but it gives young boys with Klinefelter Syndrome the best chance of having biological children in the future.

If you receive a diagnosis later in life and want children, talk to your doctor about your options. They may suggest you try assisted fertility treatments before going on to testosterone replacement therapy.

Can men with Klinefelter syndrome have biological children?

The vast majority of men with Klinefelter syndrome will find it impossible to conceive naturally. This is often when a diagnosis happens – as up until then the other signs are pretty subtle (as you can see from the list above).

Infertility in men with Klinefelter syndrome is caused by issues in sperm production – which happens for two reasons. Firstly they often have very low testosterone, a hormone essential for making sperm. They also often have underdeveloped testicles – or testicles that never dropped.

This is a perfect storm for fertility issues but there is a bit of hope. If you have a mild case of Klinefelter (the kind known as ‘mosaic’) there’s a chance you may have sperm cells in your testicles, even if you don’t have enough making their way to your semen.

If this is the case, it is theoretically possible for fertility specialists to extract sperm directly from the testicle and use any healthy sperm in assisted fertility treatments like ICSI. There are different surgical techniques called TESA (testicular sperm aspiration), TESE (testicular sperm extraction and micro-TESE (microdissection testicular sperm extraction) that can extract the sperm. It might not always be successful, but it’s thought that this is possible for around 50% of men with Klinefelter Syndrome to at least extract some sperm through this process.

What are my options if this isn’t successful?

It’s important to remember that, whilst it’s understandable to want biological children, there are many ways to build a family. Even if assisted fertility treatments aren’t possible, many men with Klinefelter Syndrome have wonderful families thanks to donor sperm. This can be a difficult concept to get your head around at first but it opens a whole world of possibilities for men struggling with infertility. You could use sperm from a bank or use a private donor – maybe a family or friend – and figure out a process and approach that works for you.

Once again, check out our interview with Gareth Landy and Sean from Knackered Knackers to hear more about the amazing experience of becoming a father through donor sperm.

A Klinefelter Syndrome diagnosis can be overwhelming at first, but there is no reason you can’t lead a happy, healthy life and become a father. For more information on the condition – head over to our friends at Living with XXY for a bunch of helpful resources and stories.

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Wearing tight pants and underwear

Studies show that men who wear looser underwear have higher sperm concentration and total sperm count compared to men who wear tighter underwear. So, lose the tight clothes and wear something loose to give your testicles some air.

CONCLUSION: learn more about how heat can affect sperm quality here.


Besides higher mortality rate and various diseases, stress is associated with low sperm quality. Stress is known to be associated with lower testosterone levels and oxidative stress with both playing an essential role in producing and maintaining healthy sperm cells.

CONCLUSION: If you feel stressed, we recommend you get some help so you can have a balanced mental health. For a stress management guide, download the ExSeed app for free and start your personalized action plan today.

Physical activity

Scientific studies show that men who are physically active have better semen parameters than men who are inactive. Fertility specialists also state that regular physical activity has beneficial impact on sperm fertility parameters and such a lifestyle can enhance the fertility status of men.

Prioritizing exercise can help improve your overall health and result in healthy, fast swimming sperm cells that have good chances of fertilizing an egg.

CONCLUSION: Try incorporating exercise in your weekly schedule to you ensure exercising at least twice weekly. We recommend a combination of cardio training and strength exercise. Read more about exercise and male fertility on our blog.


Fast Food
Processed foods damage the health of sperm-producing cells and cause oxidative stress, which lead to poorer sperm quality. Heavy consumption of junk food (every week) can increase the likelihood of infertility since men who consume vast amounts of unhealthy food are at risk of having poor sperm quality. Besides harming your fertility, junk food enlarges your waistline, harms your cardiovascular system, kidneys, and more.

Eating more fruit and vegetables can increase your sperm concentration and motility. It’s important that you consume a healthy diet filled with antioxidants and that you eat vegetables every day. Foods such as apricots and red bell peppers are high in vitamin A, which improves male fertility by nurturing healthier sperm. Men who are deficient in this vitamin tend to have slow and sluggish sperm.

Sugary snacks/beverages: several times a week Excessive consumption of high sugar items can lead to oxidative stress, which negatively impacts testosterone levels and sperm motility. Sugary snacks and beverages are also highly associated with obesity and low fertility.
CONCLUSION: To boost sperm quality, stay away from fast food, processed food, and sugary snacks or beverages. You need to implement a healthy prudent diet filled with necessary superfoods needed for good sperm production. Check out our guide to Male Fertility Superfoods. For personalized guidance and support on how you can start improving your sperm health, check out the Bootcamp.


Direct heat can inhibit optimal sperm production and cause Sperm DNA damage. Sperm cells like environments that are a couple of degrees lower than body temperature. Avoid overheating from warm blankets, seat warmers, heat from your laptop, hot showers, and saunas.

Cigarette smoking

The exposure to tobacco smoke has significant negative effects on semen quality. The damage of cigarettes and nicotine of course depends on how many cigarettes you smoke per day and for how long, but even low usage (up to 10 cigarettes / day) can inhibit healthy sperm production.  

CONCLUSION: Stay as far away from cigarette smoking as possible if you care about your general health and your fertility. Read more here.

Cell phone

When you have your cell phone in your front pocket, your testicles are exposed to electromagnetic radiation, which studies have shown to damage the sperm cells. Put your phone in the back pocket of your pants or in your jacket pocket.


There is a clear association between obesity and reduced sperm quality. At least part of the reason for this is that obese men may have abnormal reproductive hormonal profiles, which can impair sperm production and lead to infertility. 

A BMI higher than 30 can lead to several processes in the body (overheating, increase in oxidative stress in the testes, sperm DNA damage, erectile dysfunction) that can have a negative impact on male fertility. This can result in problems when trying to conceive.  

CONCLUSION: BMI is one of the risk factors that influence semen quality and, for example, sperm motility.  


A beer or glass of wine now and then do not really harm sperm quality. But excess alcohol drinking (more than 20 units per week) can reduce the production of normally formed sperm needed for a successful pregnancy.

CONCLUSION: If you want to stay safe, stay under 14 units of alcohol per week. For more information on how alcohol can affect male fertility, take a look at our blog: “Alcohol and Sperm Quality”.


Studies show that women younger than 35 and men younger than 40 have a better chance of getting pregnant. Men can produce sperm cells almost through their entire life, but the sperm cell DNA is more fragile and prone to damage after the age of 40.

As men age, their testes tend to get smaller and softer resulting in a decline in sperm quality and production. These changes are partly because of an age-related decrease in testosterone level, which plays a very important role in sperm

production. Higher male age (>40 years) is not only associated with a decline in sperm production but also with increased sperm DNA fragmentation and worsened morphology (shape) and motility (movement). These negative effects make the sperm cells less qualified for egg fertilization.

CONCLUSION: with an age under 40, you shouldn’t have to worry much about age as a factor in itself. However, studies have shown a slow decline after the age of 30-35 years

and if you are above 40 years of age, your sperm quality can be affected due to increased sperm DNA damage resulting in a decrease of sperm motility and concentration. Remember that you cannot evaluate the quality of a sperm sample by just looking at it – this requires a sperm analysis.