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KS/XXY affects around 1 in 600 males, but many medical practitioners mistakenly think that is so rare that they will never come across it. 

Early diagnosis and a good understanding of the implications of Klinefelter’s Syndrome (KS)/XXY can improve life for both the person with the condition and for those with whom they have close contact.

The effects of KS/XXY can extend well beyond infertility and a lack of testosterone. A timely diagnosis can make a huge difference to life experiences.

This poem, The Syndrome, expresses how many KS/XXY folk feel. It was written by a KSA member who was diagnosed at 70.

The importance of early diagnosis

Around 75% will never get a diagnosis

KS/XXY affects around 1 in 600 males, but many medical practitioners still think that is so rare that they will never come across it. 

 The KSA is trying to change this perception to improve rates of diagnosis.  It works to raise the profile of the condition generally, but particularly within the medical profession.

Initial tests if KS/XXY suspected

Blood tests are needed  to check levels of:
• lutenising hormone (LH) 
• follicle stimulating hormone (FSH)
• sex hormone binding globulin (SHBG)
• testosterone (T).

Tests for testosterone levels should be taken early in the morning (around 8.00 am to 9.00 am). Levels taken at different times of the day will be lower and less reliable.

Test results

Normal ranges for adult males:

  • FSH     1.6 – 11.0 mIU/mL
  • LH       1.3 – 8.0 mIU/mL
  • SHBG   13 – 71 mmol/l

Normal testosterone levels are between 9.9 and 28.5 nmol/l. Readings will vary between laboratories.

High LH, FSH, SHGB and low testosterone levels indicate that the testes are producing little or no testosterone.

This is called hypogonadism and may indicate KS/XXY, although it can have other causes. A genetic blood test is needed to confirm the diagnosis.

The type of hypogonadism which occurs in KS/XXY is called primary hypogonadism i.e. it is caused by a problem with the testicles themselves.

LH, FSH, SHBG and testosterone

LH stimulates testosterone production from the testicles. Testosterone in turn regulates LH secretion by a process called ‘negative feedback’. LH secretion is therefore under restraint from testosterone. Similarly, FSH stimulates sperm production in the testicles, as well as stimulating production of inhibin B from the testicles. The latter is responsible for, by negative feedback,  restraining FSH production from the pituitary.

When the testicles are severely damaged, both testosterone and inhibin B production are reduced, removing the restraint of these hormones on the hypothalamus and pituitary, leading to high levels of LH and FSH. The LH and FSH levels are higher than normal because the pituitary is working ‘extra hard’ to try and stimulate the testes, which are not responding because they are either damaged or absent.

Trigger times for diagnosis


During pregnancy.
If screening was carried out for Down’s Syndrome etc. the extra chromosome may be discovered.


KS/XXY babies often have uni- or bi-lateral cryptorchidism (undescended testicles).

They may present as ‘floppy’ babies and have difficulty feeding due to poor muscle tone.

Currently, there is no ante-natal screening programme for KS/XXY


Pre-school, if the child has a language delay or disorder. This is the most common problem for children. Speech therapy can make a considerable difference. As they are visual thinkers, diagrams, charts and colours will make life easier.

Before puberty

During schooling, if the youngster is having difficulties either socially or academically.

Often youngsters become frustrated because they find it difficult to express themselves and have problems processing information.

Everything seems to take longer and they are often perceived as being stupid and lazy – when they know they are neither!

They are visual thinkers so diagrams, charts, colours and written instructions will make life easier.


Young adults are likely to become aware that their genital area is not developing in the same way as their peers.

There might be some breast development and puberty may be slightly delayed.

Social awkwardness may become a problem and they may find it difficult to relate to their peers.

Libido may be low and various behaviour issues might become apparent as they struggle to ‘fit in’.

They are often immature for their years and can be very vulnerable.

Fertility investigation

Many cases of KS/XXY are diagnosed following infertility investigations. This can be a very difficult time and often little support, or even information, is offered.