Turner syndrome

Turner syndrome is a human genetic abnormality, caused by a defect in the sex chromosomes. Instead of the normal XX or XY sex chromosomes, only a single X chromosome is present. In Turner syndrome, female sexual characteristics are present but underdeveloped. People with Turner syndrome often have a short stature, webbed neck, low hairline, abnormal eye features and bone development and a "caved-in" appearance to the chest.

Turner syndrome is a disorder caused by the loss of genetic material from one of the sex chromosomes.

Humans normally have a total of 46 chromosomes (which are tiny, DNA-containing elements) that are present in every cell of the body. DNA encodes genes, which specify all the proteins that make up the body and control its functions.

In humans, there are 23 matched pairs of chromosomes in every cell. Each cell contains 22 pairs of chromosomes called autosomes that are the same in males and females. The remaining pair of chromosomes, the X- and Y-chromosomes, are not shaped similarly, and thus are not matched in the same way as the autosomes.

The X- and Y-chromosomes are called sex chromosomes. They are responsible for the difference in development between males and females. A Y-chromosome contains genes responsible for testis development; and the presence of a X-chromosome paired with a Y-chromosome will determine male development. On the other hand, two X-chromosomes are required for normal ovarian development in females.

What can be done?

As a chromosomal condition, there is no "cure" for Turner syndrome. However much can be done to minimize the symptoms. For example:

• Growth hormone, either alone or with a low dose of androgen, will improve growth and probably final adult height. Growth hormone is approved by the Food and Drug Administration for treatment of Turner syndrome and is covered by many insurance plans.

• Estrogen replacement therapy has been used since the condition was described in 1938 to promote development of secondary sexual characteristics. Estrogens are also important for maintaining good tissue and bone integrity.

• Modern reproductive technologies have also been used to help women with Turner syndrome become pregnant if they desire. For example, a donor egg can be used to create an embryo, which is carried by the Turner syndrome woman.

External links

• http://turners.nichd.nih.gov/
• http://www.turner-syndrome-us.org/