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Sep 06, 2006
Turner's Syndrome
by SirGan|
Turner's syndrome is one very specific chromosomal abnormality which is characterized by absence of all or part of one X chromosome. Many people have heard about it but not too many of them know that - it has been described in many species, including humans, mice and horses. It is important to point out that individuals with this disorder have a female phenotype or female physical appearance, have abnormalities in reproductive function as well as a number of other clinical manifestations of disease.
Possible causes of the conditionThere is no doubt- problem is in malformations of genes? What exactly are these genes? Well, everyone should know that genes are literally the blueprint for human bodies- factors such as growth, development and functioning. Humans have 46 paired chromosomes, with two sex chromosomes that decide gender. Other 44 chromosomes dictate other factors. The most important fact is that a female has two X chromosomes. However, in females with Turner’s syndrome, one of these chromosomes is absent or abnormal. The missing genes cause the range of anomalies and symptoms associated with this condition.
Incidence of the conditionNot too many people know that the Turner's syndrome is the most common sex chromosome abnormality of human females. Researches who that the incidence of this disorder, in newborns, is approximately- 1 in 2,500. However, roughly 10% of spontaneously aborted fetuses have this disorder and the incidence has been estimated as 0.8% in zygotes, making it possibly the most common chromosomal disorder in man. It is important to point out that almost half of the females with Turner's syndrome have X chromosome monosomy (45, X). In roughly 2/3 of cases having a 45,X karyotype, the single X chromosome is of maternal origin. What's interesting - at least two X-linked genes known to not undergo inactivation in man do undergo inactivation in mice.
Clinical characteristicsFemale phenotypeLike it was already been told- this characteristic is caused by the absence of a Y chromosome. That’s why- it is proven that patients with Turner syndrome may have:
Short statureEvery patient should know that in most cases- weight and height at birth are below the normal values.
Sexual infantilismThere is no doubt- this characteristic is caused by rudimentary ovaries. It should be pointed out that sexual ducts and external genital structures appear like normal females, but only very immature. Experts are claiming that when examined at birth- the gonads are long, pale streaks of tissue devoid of primordial follicles. Early in gestation the gonads appear normal and contain primordial germ cells, but after the third month, numbers become severely reduced and, in most patients oocytes are not present after birth.
A variety of somatic abnormalitiesFrequently observed abnormalities include:
Kidney problemsIt is extremely important to point out that kidney problems are present in approximately 1/3 of individuals with Turners. Big problem is that these problems may contribute to high blood pressure. Three types of kidney problems have been reported:
OsteoporosisSeveral researches done in the past have shown that there is a high incidence of osteoporosis. This is condition characterized by thin or weak bones. There is a big problem with this condition because it can lead to loss of height, curvature of the spine and increased bone fractures.
The primary cause of osteoporosis in individuals with Turners appears to be inadequate circulating estrogen in the body.
IntelligenceGood thing is that normal intelligence is very common characteristic in individuals with Turner's syndrome but- a majority have some type of learning disability, often involving visual-spatial skills.
Premature menopause issueEvery patient should know that, since the X chromosomes dictate female physical characteristics, it is logical to assume that missing genes interfere with sexual development. The worst possible complication is infertility which is caused by the failure of the ovaries to grow properly. There is a great majority of patients which then undergo a premature menopause. There may be some eggs present at birth but these degenerate soon after. Unfortunately- only around 5 to 10 per cent of girls with Turner’s syndrome menstruate naturally. Bad thing is that all the rest need hormone replacement therapy.
Diagnosis of the conditionPrenatal diagnosisIt is important to know that Turner's syndrome is commonly diagnosed prenatally. It also happens often in women undergoing amniocentesis or chorionic villus sampling for other reasons. Several researches done in the past have showed that advanced maternal age does not seem to be a risk factor by itself for this disorder.
UltrasonographyEvery patient should know that ultrasonography is one very valuable tool for detecting fetuses with Turner's syndrome. What are the results of this test? Well, typical findings include:
Other test
Treatment optionsUnfortunately- every patient or patient’s relative should know that Turner’s syndrome is a lifelong condition but- good thing is that there are many treatment options which are there for helping affected women reach their potential in all aspects of life. The goal of good treatment is to correct any physical defects and help bring about puberty. Most common treatments are:
Medical consequences of Turner syndromeCardiovascular problemsExperts are saying that several researches done in the past showed a significantly greater number of deaths from diseases of the circulatory system than expected.
Thyroid problemsIt is important to know that approximately 1/3 of individuals with Turner syndrome have a thyroid disorder. We are usually talking about usually hypothyroidism. Symptoms of this condition include:
In most cases, this disorder is caused by an immune system attack on the thyroid gland. This type of thyroiditis is also known as Hashimoto's thyroiditis. Although it is not known why thyroid disorders occur with a high frequency in Turner syndrome, good thing is that the condition is easily treated with thyroid hormone supplements.
Type II diabetesSeveral researches also showed that type II diabetes, also known as insulin resistant diabetes, has a high occurrence rate in individuals with Turner syndrome. Patients which suffer from this syndrome have twice the risk of the general population for developing this disease. Unfortunately- the reason for the high risk of diabetes amongst individuals with Turner syndrome is unknown. Good thing is that diabetes type II can be controlled through careful monitoring of blood-sugar levels, diet, exercise, and medication.
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