Klinefelter's Syndrome

Klinefelter's syndrome, also known as 47,XXY or XXY syndrome is a genetic abnormality in which boys and men have an extra X sex chromosome. This means men show a pattern of XXY in their sex chromosomes instead of XY. (This is not the same as XYY syndrome.)

Klinefelter's syndrome (KS) is actually the most common sex chromosome disorder, and is found in about 1 out of every 500 male births.

The major effects are small testicles and a reduction in fertility. However, there are many other physical and behavioral effects, though the seriousness of these varies, and indeed many boys and men with Klinefelter's show few detectable symptoms.

If you have Klinefelter's please consider sending us some information about how it has affected your life and some photos to help other men in the same us on
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Signs and symptoms

KS men are nearly always infertile although some modern fertility treatments may help in conception. There may be language learning impairment or issues with other neural functions.

Bodily characteristics include a range of symptoms from little or no differences to the 46XY male, all the way through to a tall, thin build and youthful facial appearance, or a rounded, less classically masculine body shape with some degree of gynecomastia (breast tissue development).

It's been suggested that the more severe symptoms of KS include testicular cell tumors, breast cancer, and osteoporosis, pulmonary disease, varicose veins, diabetes mellitus, and rheumatoid arthritis, but there is some doubt about the association.

"Hypogonadism" in XXY men refers to the very common decreased testicular hormone production (testosterone) or reduced endocrine function. Men with XXY chromosomes often have a low level of testosterone in their blood but high pituitary hormone levels - FSH and LH.

However, the most obvious symptom of KS, or "XXY men", is often their small and incomplete testicular development.

There are many variations of XXY abnormalities. The only reliable method of identification is karyotype (gene/chromosome) testing and identification. This is done using a small blood sample containing white blood cells, which are cultured in vitro and then checked for chromosomal discrepancies or abnormalities, such as the extra X chromosome of KS.

This can also be done before birth, and in 2002, it was found that about half of embryos showing KS in the USA were terminated.


The genetic make-up of the cells cannot be changed. However, testosterone treatment is a good option for men who want to look more masculine. This can counteract hypogonadism, depression, and anxiety, as well as the physical effects of low testosterone, including osteoporosis.

A man with Klinefelter's Syndrome writes:

I was told at about age 19 that my testicles were smaller than they should be. That gave me an insecurity that I still carry to this day. I drowned it in alcohol and sex with the lights out for years.

In between those "episodes" I went to prison. (The only job that was going to support me while being drunk every day was drug dealing.) I was diagnosed at age 26. I had a lump on my testicle in the prison. I told them I wanted to know if the lump was cancer (it turned out not to be) and why they were so small.

Klinefelter's Syndrome (KS) was diagnosed through taking a blood sample. KS is an extra chromosome in the 23 pair of chromosomes. Those are the sex chromosomes. (If you're thinking Down's Syndrome, you're off. Down's is an extra chromosome in the 21 pair.) A normal male is XY; a female is XX, and Klinefelter's is XXY.

I don't have female sex organs although extra breast tissue is common and KS men should be screened for breast cancer. (By the way KS men are usually taller than other men in their family. I'm 6'6". The X chromosome carries a growth gene.) There are learning problems associated with KS, particularly language. There are cases of KS with more than one extra X; with every extra X the chances for mental retardation increase.

As you know, DNA is in every cell of our bodies. There is a such thing as KS mosaic where some of the cells in the body are a normal 46XY and others are 47XXY. I have 47XXY throughout. This often means a guy has low testosterone - fortunately the doctors started me on testosterone (T) injections. Men with low T usually have a shorter and poorer quality of life.

There are so many things that can go wrong with low T levels. Osteoporosis and rapid muscle degeneration as one ages were the two main ones the doctors warned me about when they started me on T therapy.

I've been on T injections for 7 years now. My testicles will never mature but the rest of me sure has. Now if you were to look at me, you'd never know about KS. I appear very masculine.

I was tall and skinny my whole life. When I started getting the T I started lifting weights and gaining size. I still lift today. It's part of what's keeping me clean/sober crime free. I now weigh 240lbs and not very much is fat. Seven years of T injections and lifting weights have turned me into a house!

This reader has kindly supplied these additional details. His flaccid penis is 3.5 inches long and 8 inches when erect. His testicles are small (click to expand the image):

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