Consult SID

Symptoms, Indicators and Diagnosis (SID)

Much of the information available about XXY/Klinefelter’s Syndrome is related to how it affects males because the syndrome was first identified in a group of males. Consequently, SID concentrates on the affect low or zero testosterone has on males. But as in the general population there are people who have XXY who do not consider themselves to be male; more research is needed to determine how XXY affects these people as they may require different medication, such as oestrogen in preference to testosterone. As that data becomes available the KSA will add to these pages. A newly created website that provides useful information for those who do not consider themselves male can be found at the XXY Brain Trust

In describing the symptoms associated with KS the KSA has used extracts from its Members Binder, from other KSA publications, desk based research and from polls conducted via the KSA’s international talk forum


The KSA gratefully acknowledges the award of a grant from the British Society of Endocrinology without which the Consult SID pages would not have been feasible.

How does KS affect a man?

Low testosterone

Klinefelter’s Syndrome (KS) is characterised by low testosterone levels as the testes do not function properly. Teenagers and young adults often have average to low levels but these decrease although some men may continue to have levels within the normal range.

Low testosterone causes decreased energy levels,  low motivation and lack of muscle bulk and strength. There is a tendency to be overweight and  female breasts may develop.

Not surprisingly, self-esteem is likely to be affected.That is the difference a lack of testosterone makes and is the reality of life for many men with KS because their bodies do not produce testosterone.

Learning difficulties

Those with KS are often labelled as lazy and lacking in intelligence. However findings from magnetic resonance imaging (MRI) studies in KS show structural abnormalities of brain regions which are connected to social understanding and emotion perception and which are related to language and communication impairments.

As language and communication affects all areas of learning and life it is not surprising that learning difficulties are common despite normal non-verbal IQ levels.





Emotional difficulties

Those with KS are less able to identify and verbalise
the emotions they experience and are also  less able to identify emotions when expressed in tone of voice. In addition they are often more emotional than is usual for men.

Again these difficulties appear to be linked to the abnormalities in some brain regions.

Poor social skills

Klinefelter men appear to be less accurate in perception of social emotional cues such as identification of facial expressions and gaze direction. The lack of these skills will contribute to decreased social competence and difficulty establishing successful social interactions and  in coping with social situations.


The symptoms of  KS vary considerably between individuals.  The severity of the condition can also be associated with the number of extra X sex chromosomes present.

The most common symptoms
  • Very small testes/low levels of testosterone
  • Infertility
  • Low sex drive/libido
  • Gynaecomastia (female type breasts)
  • Poor social skills
  • Low self-esteem
  • Poor short term memory
  • Difficulty processing verbal information
  • Poor communication and organisational skills
  • Unexplained tiredness or lethargy
  • Tall stature with disproportionally long legs and arms
  • Lacking or sparse body and facial hair
  • ‘Female type’ body shape and fat distribution
  • Flabby or poor muscle tone especially upper body
  • Low bone density
Other features associated with KS
  • Varicose veins of the lower legs and poor circulation
  • A predisposition to thrombosis
  • Depression and mood swings
  • Urinary tract infections
  • Migraines
  • Autoimmune disorders
  • Osteoporosis
  • Increased risk of breast cancer
Common symptoms in children
  • Speech and language development disorders
  • Poor concentration skills
  • Lack of agility and dislike of physical games, especially team games
  • Passiveness/shyness
  • Difficulty with self expression
  • Moderate learning difficulties

Although low intelligence was once seen as a symptom it is more likely that the speech and language development disorders, in addition to the other symptoms listed above are the cause of the learning difficulties. Most of those with KS are within the normal intelligence range although they may require more targeted support and effort then their peers. A highly useful publication, available via the Free Downloads, is “The Learning Needs of Boys with KS: Information for Teachers and Parents” by Paul Collingridge.

Another point of view is that children diagnosed with KS develop at a slower rate than other children. To quote Onnineko of

"The development time of the typical person is very short. It is well known that a child learns both better and faster than an adult. An XXY child develops over a period considerably longer than an XY or XX child, about 8 more years. Society for 99% of the world believes that at 18, the child is mature. However, XXY children mature at about age 25. If we compare an XXY child at their point of relative maturity at age 25 to an 18 year old, the 25 year old child is significantly higher on intelligence tests."

Effects of KS as reported by members of, the KSA's international online talk forum
Younger looking and acting than actual age299
Uncommonly gentle, caring, sharing, and intuitive288
Lower degree of self esteem275
Reduced facial hair – reduction in need to shave / reduced body hair266
Depression or tendency toward it260
Reduced muscle power and stamina250
Height taller than average (avg. is 5 ft. 10 in. for USA Caucasian males)248
Difficulty in concentrating244
Incomplete masculinisation; feminine, or pear shaped body and body hair distribution244
Introversion and frequently shy239
Taller than fathers and brothers235
Decreased serum testosterone levels232
Life-long soft skin230
Decreased libido215
Anxiety and neuroses214
Change in body shape – increased fat and breast development212
Abnormal body proportions (long legs, short trunk)211
Gynaecomastia now or in the past207
Preference for quiet games when as a child197
Restless sleep pattern196
Rounded shoulders and rounded hips192
Difficult to awaken in the mornings185
Behavioural problems, including aggression and non-participation in social activities178
Frustration-based outbursts175
Emotional and mental disorders150
Non lateral thinker — visual spatial thinker150
The inability to maintain long term friends142
Learning disabilities especially language difficulties138
Sexual confusion138
Smaller than average erect penis (avg. is approx. 14 cm — 2.54 cm = 1 inch)129
Hand tremors128
To some degree, euneuchoidal stature (arm span is usually 2 inches longer than height)119
Erectile dysfunction and/or impotence117
Gender confusion105
High cholesterol problems99
Decreased bone mineral density in adults96
Minor bony abnormalities e.g. in hands and elbows95
Attention Deficit disorder94
Inner anger, requiring anger management93
Motor skill issues89
Taurodontism with teeth having a thinning of the surface and enlargement of the pulp82
Sleep apnea79
Cardio-vascular problems67
Dyslexia (physical)65
Increased serum luteinizing hormone52
Increased serum follicle stimulating hormone50
Loss of sense of smell51
Osteoporosis – brittle bones resulting in fractures43
Adult onset diabetes mellitus30
Simian crease (single crease in the palm)24
Venous disease23
Benign Prostatic Hyperplasia16
Arteriosclerosis (hardening of the arteries)13
Autoimmune disorders such as lupus and Darier’s syndrome13
Myocardial Infarction after the age of 30 is common10