Turner Syndrome

Definition – what is the Turner syndrome?

Turner syndrome, also known as Monosomy X and Ullrich-Turner syndrome, is a genetic disorder that affects only girls. It was named after its discoverers, the German pediatrician Otto Ullrich and the American endocrinologist Henry H. Turner. Characteristic signs of the Turner syndrome are dwarfism and infertility.

Turner syndrome is the most common form of gonadal dysgenesis (malformation of the gonads). It is assumed that about 3% of all embryos are affected, but a large proportion of them die intrauterine. It is assumed that every tenth spontaneous abortion in the first trimester is due to Turner syndrome. The frequency of Turner syndrome in the population is about 1:2500-3000.

Causes

The Turner syndrome is based on a maldistribution of the sex chromosomes. Normally, humans have 46 chromosomes, on which genetic information is stored. These include two sex chromosomes: in women two X chromosomes (46, XX) and in men one X and one Y chromosome (46, XY).

In girls with a Turner syndrome, the second X chromosome (45, X0) is missing. Therefore, this is also called monosomy X. In about 30% of the cases, there is also a non-functional second X chromosome.

A mosaic variant is also possible and occurs in 20% of cases. This means that only in some cells of the body the second X is missing or not functional. The Turner syndrome is not hereditary.

The exact cause of the chromosomal abnormality is not yet known. It is suspected that the cause lies in the maturation of the paternal sperm. There is no connection between the occurrence and the age of the mother, unlike, for example, in trisomy 21.

Diagnosis

A Turner syndrome can be diagnosed before birth, e.g. by amniocentesis or sampling of the placenta. However, these examinations carry risks for the pregnant woman and are not performed routinely. Non-invasive blood tests (prenatal test) can also be used to diagnose Turner’s syndrome.

However, these are very expensive and are also not part of the standard diagnostics. After birth, Turner’s syndrome is most noticeable because of the small stature of the affected girls. If the disease is suspected, an examination should be performed with regard to further physical changes.

Further diagnostics should also be performed to look for malformations of the internal organs (heart ultrasound, ultrasound of the urinary tract). Furthermore, the concentration of various hormones in the blood can be determined. In Turner’s syndrome, the estrogens are lowered and the luteinizing hormone (LH) and the follicle-stimulating hormone (FSH) are increased (hypergonadotropic hypogonadism). Furthermore, the blood cells can be subjected to a chromosome analysis and thus a missing X-chromosome can be detected.