XX Male Syndrome
Name: Karin Chuoke
Country: United States
Date: December 2005
If a male is born with XX sex chromosome (XX Male syndrome),
What characteristics can be expected from these individuals?
Occasionally an individual receives the incorrect number of chromosomes.
Most of these combinations are lethal, and the mother may not even know that
she is pregnant before the very young embryo is passed in what appears to be
a normal menstrual flow. In a few cases, the unusual combination is viable.
Down's syndrome, for example, results when an individual has three copies of
chromosome 21, instead of the usual two. Another example is when individuals
receive the incorrect number of copies of the sex chromosomes, X and Y.
A variety of combinations have been observed: XXY, XXX, XYY, etc. In the
case of XXY individuals, the person has what is called Klinefelter Syndrome.
Many of these individuals are capable of sexual intercourse, but they are
often sterile, due to underdeveloped testes. A lower than normal amount of
testosterone is produced, leading to lowered amounts of muscle mass and
lowered energy levels compared to XY males. The body may show some feminine
traits, e.g., partial development of breast tissue, lack of facial hair,
etc. The brain structure is altered somewhat, and learning disabilities may
be observed. These days, XXY males can be given testosterone shots during
puberty, to counteract the low levels of testosterone produced.
The presence of abnormal numbers of sex chromosomes is not related to
homosexual tendencies. In other words, homosexual individuals do not have
abnormal chromosome numbers, and Klinefelter individuals are not necessarily
Paul Mahoney, PhD
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Update: June 2012