The future gender of the individual coming into being is already fixed on a chromosomal level during the fertilization of the ovum. The determination and differentiation of the gender take place during the embryogenesis. Disturbances of the sexual differentiation can arise due to chromosome anomalies, gene mutations and exogenous or endogenous influences, which are remarkable at last in the puberty and cause patients to consult a doctor.
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Human sex chromosomes

Picture: “Human sex chromosomes” by Openi. License: CC BY 4.0

Definition, Epidemiology, and Etiology of the Turner Syndrome

An important disorder of the genital development is the Turner Syndrome which is defined by a chromosomal aberration. It is a gonosomal monosomy which means that there is only one of the two gonosomes, in this case, the X-chromosome. The result is the karyotype 45, X0 with a female phenotype.

It is the only monosomy which is bearable in a human’s life and is with a frequency of 1 : 2500-7500 (living girls) the most frequent gonadal chromosome anomaly for women. The syndrome accompanies a high spontaneous abortion rate.

The cause is the loss of a gonosome during the embryogenesis which can occur on different levels of the development (spermatogenesis or oogenesis, fertilization) and is based on a nondisjunction of the chromosomes, more specifically of the chromatids. In 70% of the cases, this gonosome is the X-chromosome of the father.

A structurally modified X-chromosome can be a cause as well. Chromosomal mosaics with unobtrusive and striking cells (e.g. 46, XX/45, X0) can also occur, but the form of the pathology is in this case proportionally weakened.

While the occurrence of the Turner syndrome does not correlate with the age of the mother, a high age of the father plays a possible role in the pathogenesis.

Symptoms and Clinical Appearance of the Turner Syndrome

In the case of the Turner Syndrome, the phenotype, as well as the psychosexual setting, are female. Main symptoms are primary amenorrhoea and dwarfism (143-147 cm). The patients are infertile and show sexual infantilism (hypoplastic female genitals due to lack of hormonal stimulation). While the gonads develop normally at first, they start to degenerate and fibrosis in the third month of pregnancy, which finally causes the ovaries to exist only as tissue cords (streak gonads).

Further facultative symptoms are:

  • Short neck
  • Pterygium colli (webbed neck)
  • Low hairline
  • Lymphoedema on the back of the hand and the foot (in the first weeks of life)
  • Cubitus valgus (x-formed arms)
  • Shield thorax with widely diverged nipples and funnel chest
  • Multiple (benign) pigment naevi
  • Nail and ear dysplasia
  • Malformations of the kidneys and the urinary system
  • Malformations of the skeleton (e.g. deformities of the spine) and anomalies of the ligamentous apparatus
  • Heart defect: e.g. aortic stenosis, aortic coarctation, anomalies of the pulmonary veins

These symptoms do not necessarily occur together and can be pronounced to a different extent according to the individual person. The intelligence of the affected persons can be normal or reduced. There are often partly inefficiencies (e.g. mathematics, spatial orientation).

As already mentioned above, fewer corporal anomalies can occur with the presence of a chromosomal mosaic. Depending on the obtained ovarian function, a puberty development and even a spontaneous pregnancy are possible (but: elevated abortion rate, congenital malformations of the children).

Diagnostics and Differential Diagnostics of the Turner Syndrome

The amenorrhoea and the absence of the puberty are often the reasons why patients consult a doctor.

Too little estrogen are produced due to the insufficiency of the ovaries, which triggers superior centers to produce more hormones. Correspondingly, there are raised levels of FSH, LH as well as a reduced level of estrogen found during an endocrinological examination. As the disorder lies on the level of the gonads, it is also called hypergonadotropic or primary hypogonadism.

To make a diagnosis, a chromosomal analysis is appropriate which is made on the peripheral lymphocytes. The karyotype of the patient can be examined with the karyogram.

The differential diagnosis has to exclude tumors (e.g. gonadoblastoma, dysgerminoma).

Therapy of the Turner Syndrome

The Turner Syndrome is not curable due to the disorder on the molecular level (missing chromosome), which is the reason why the treatment only allows for a symptomatic therapy which improves the physical and psychic female characteristics.

A hormone substitution is induced in the beginning of the puberty (approximately at the age of 12 or 13). Estrogens enhance the growth of the primary and secondary sexual characteristics (vagina, uterus, breast development, pubic hair) and provide prevention of osteoporosis and arteriosclerosis. A preparation which is used is, for example, estradiol valerate (1-2 mg). Gestagens should be given at least ten days a month as they trigger the menstruation. Hence the endometrium is transformed and not constantly stimulated which prevents the development of an endometrium carcinoma.

The final height of the patients can be increased by up to 10 centimeters through the early dose of a synthetic growth hormone (hGH). But this should already take place in the early childhood.

The infertility of affected women cannot be healed. But an egg donation can be considered when desiring to have children.

Note: The sterility of patients with the karyotype 45, X0 is irreversible.

A surgical therapy for the removal of disturbing stigmata (e.g. Pterygium colli) comes into question as well. A psychosocial care for the patients is important, too.

Complications of the Turner Syndrome

Women which suffer from the Turner Syndrome come down more frequently than the standard population with cardiovascular diseases, diabetes mellitus, thyroid diseases and inflammable bowel diseases.

The lifespan of the patients can be reduced by 13 years on the average.

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