i have a biology report that i have to type up, and i need some information on Turner's Syndrome.
i need to know such things as: what chromosome the disease is on?, how the disease does what it does, how and why?, what the impact on the organism is?, and how common it is?.
can anyone help me??? please? Type it up in your yahoo search bar, or google it. Another great source is wikipedia on the internet. You should find everything you're looking for and more. http://www.turner-syndrome-us.org/resour... What is Turner syndrome?
Turner syndrome (TS) is a chromosomal condition that describes girls and women with common features that are caused by complete or partial absence of the second sex chromosome. The syndrome is named after Dr. Henry Turner, who was among the first to describe its features in the 1930s. TS occurs in approximately 1 in2,000 live female births and in as many as 10% of all miscarriages.
How is Turner syndrome diagnosed?
Diagnosis is made through a test called a karyotype, which is usually performed on cells in the amniotic fluid before birth and on cells in the blood after birth. A trained specialist countsthe chromosomes in the white blood cells and looks for abnormalities. Females normally have two X chromosomes (46,XX) and males have one X and one Y (46,XY). Turner Syndrome individuals are missing all or part of one of their sex chromosomes. About half of girls with Turner syndrome have only one X chromosome (45,X). Another third have two X chromosomes, but part of one X is missing. Other individuals with Turner Syndrome have a mosaic pattern: some of their cells are missing an X chromosome (45,X), while other cells have different chromosome composition (such as 46,XX)
Turner Syndrome may be diagnosed throughout the life span, including adulthood, if signs are subtle. Signs that indicate a karyotype is needed can include:
* Fetal abnormalities such as cystic hygroma (fluid around the neck), or incidentally when a routine amniocentesis is performed (e.g., for advanced maternal age)
* Webbed neck or lymphedema (swelling of hands and feet) in newborns
* Specific heart problems in infants
* Slow growth and/or short stature
* Delayed puberty or amenorrhea (lack of menstrual cycles)
* Infertility or menstrual irregularities.
What are the primary characteristics of Turner syndrome?
Short stature
The most common feature of Turner syndrome is short stature. The average height of an adult TS woman who has received human growth hormone treatment is 4鈥?鈥? Individuals tend to be a little shorter at birth, averaging 18.5鈥?compared to an average of 20鈥?for all girls. Growth failure continues after birth, and most girls with TS fall below the normal female growth curve for height during early childhood. TS girls who are not treated with hormone replacement usually do not have a pubertal growth spurt; many will continue to grow at a slow rate until they are in their twenties. Many girls who undergo growth hormone treatment have been able to achieve adult height within the lower range of normal.
Premature ovarian failure
Most (90%) TS individuals will experience early ovarian failure. The ovaries produce eggs and hormones necessary for the development of secondary sexual characteristics. Estrogen replacement therapy is necessary for breast development, feminine body contours, menstruation and proper bone development. About a third of TS individuals will show some signs of breast development without estrogen treatment; however, many will not complete puberty, and those that do often have premature ovarian failure. Therefore, the majority of individuals will require estrogen from puberty until the normal age of menopause. Fertility without assisted reproduction therapy is rare (less than 1%).
Physical features
Many characteristic features are associated with Turner syndrome. Their presence and severity vary greatly from individual to individual.
* Narrow, high-arched palate (roof of the mouth)
* Retrognathia (receding lower jaw)
* Low-set ears
* Low hairline
* Webbed neck
* Slight droop to eyes
* Strabismus (lazy eye)
* Broad chest
* Cubitus valgus (arms that turn out slightly at the elbows)
* Scoliosis (curvature of the spine)
* Flat feet
* Small, narrow fingernails and toenails that turn up
* Short fourth metacarpals (the ends of these bones form the knuckles)
* Edema of hands and feet, especially at birth
* Intelligence - TS individuals are on average of normal overall intelligence with the same variance as the general population. They do, however, often have difficulty with spatial-temporal processing (imagining objects in relation to each other), nonverbal memory and attention. This may cause problems with math, sense of direction, manual dexterity and social skills. New and better ways to compensate for these problems, which fall under the general category of nonverbal learning disabilities, are being researched.
What are the associated risks with Turner Syndrome?
Several medical problems occur more frequently in individuals with Turner syndrome than in the general population. It is important that TS individuals are screened regularly to see if any of these problems exist. Most of these conditions can be managed successfully with good medical care.
Heart
Some form of cardiac abnormality occurs in approximately one-third of TS patients. Problems are primarily left-sided and may include coarctation (narrowing) of the aorta and bicuspid aortic valve (a valve with two leaflets instead of the usual three). TS individuals are also at higher risk for hypertensionor high blood pressure. TS patients should receive an echocardiogram or MRI to evaluate the heart at the time of diagnosis regardless of age and have their heart re-evaluated periodically for aortic root enlargement. All individuals with TS should be aware of the symptoms of dissection of the aorta, an uncommon but life-threatening complication. These include sudden, severe, sharp, stabbing, tearing, or ripping chest pain, intense anxiety, rapid pulse, profuse sweating, nausea and vomiting, dizziness, fainting or shortness of breath.
Kidney
Thirty percent of TS individuals will have kidney abnormalities. Many of the abnormalities do not cause any medical problems; however, some may result in urinary tract infections and an increased risk of hypertension. It is recommended that TS individuals receive a renal ultrasound examination at the time of diagnosis.
Thyroid
Hypothyroidism (low level of thyroid hormone) caused by autoimmune thyroiditis (inflammation of thyroid gland) occurs frequently in individuals with TS. It can be diagnosed with a blood test and is easily treated with thyroid hormone.
Ears
Otitis media (ear infection) is extremely common in TS girls particularly in infancy and early childhood. Aggressive treatment of infections is appropriate. The majority (50-90%) of TS women will also develop early sensorineural (nerve) hearing loss and may require hearing aids earlier than the general population.
How can Turner Syndrome be treated?
The treatment of TS individuals should be individualized; physicians, family and patients should decide on treatment options together.
Growth hormone therapy
Human growth hormone (hGH) is an FDA-approved drug used to increase the growth rate and achieve greater final height in TS patients. Therapy should be considered when a TS individual experiences growth failure and/or drops below the 5th percentile of the normal female growth curve. The expected increase in height depends upon many factors, including how early GH is started, what dose is given, the duration of treatment, if anabolic steroids (such as oxandrolone) are also given, and how late estrogen therapy is begun. Gains in height between 5 and 16 cm (2 and 6 inches) have recently been reported; however, not every individual responds to growth hormone. Treatment is discontinued when growth is very slow(less than 2 cm or 1 inch per year) or if the patient has reached a satisfactory height.
Estrogen therapy
This therapy isnecessary in most TS individuals because of ovarian failure. Therapy is typically begun at 12-14 years of age but should be individualized to optimize both growth and pubertal development. Estrogen is given in small doses to initiate puberty and breast development. The dose is then increased and progesterone is added in order to initiate a monthly menstrual cycle. TS individuals can experience normal sexual function on estrogen therapy. Because of the role estrogen plays in maintaining healthy bone mass, it is generally recommended that the therapy continue untilthe age of normal menopause around 50.
Becoming a family
Many options are available to TS women who wish to have children. The most common fertility solution for TS women is adoption. There are now also assisted reproduction technology options for TS women who wish to become pregnant. They include in-vitro fertilization with egg donation by a related or anonymous donor or donor embryo transfer. It is critical that a TS patient undergo a thorough physical evaluation (particularly cardiac and renal) before attempting pregnancy.
With the help of medical specialists and a good social support system, a woman with Turner syndrome can live a happy, healthy life.
Posted December, 2005
GENETIC OVERVIEW OF TURNER SYNDROME
Turner Syndrome (TS) is a chromosome abnormality affecting about 1 in every 2,000 female births and up to10% of miscarriages. TS is characterized clinically by short stature, ovarian failure, and a variety of other features such as extra neck skin, heart abnormalities, mild hearing loss, and others.
Genetically, TS is due to the absence of all or part of onesex chromosome, usually one X. This abnormality, also called monosomy X, is denoted medically as the 45,X (older literature used XO) karyotype, as opposed to the usual 46,XX female karyotype. Many, perhaps most, girls and women with TS are actually mosaic, meaning that they have cells with more than one karyotype. Oftenthere is a mix of 46,XX and 45,X cells, and in this case the resulting clinical abnormalities tend to be milder than in 45,X TS. Mosaicism, especially 45,X/46,XX, is frequently detected by prenatal diagnosis (amnicentesis). Occasionally there is mosaicism for cells containing Y chromosome material - but not enough to cause male sexual features. Girls with TS and Y chromosome mosaicism are at increased risk of developing a tumor of the gonads and should have their nonfunctioning ovaries removed.
Molecularly, most TS features result from having one rather than two copies of certain X chromosome genes. To date, one gene called SHOX has been clearly implicated in TS. Loss of one copy of SHOX is the main cause of short stature in TS. Identification of TS genes may lead to better treatments for short stature and other symptoms.
This article was provided by Dr. Andrew Zinn, Chair of the Medical Advisory Board.
Posted December, 2005
GROWTH IN TURNER SYNDROME
Growth in Turner syndrome (TS) is decreased, and on average the girl with TS will grow to be 8 inches (20 cm) shorter than she would have been. This is because at least one of the genes that influences growth, the SHOX gene, located on the very ends of the short arms of the X chromosomes, is usually missing andaccounts for much of this growth deficit. The growth decrease can be present at birth, with the infant being just bit smaller than average, and proceeds to become more obvious by two to three years and gradually more obvious thereafter. At the time of puberty, whether the girl has some of her own estrogen or takes it as replacement, the growth spurt is much less than average. Each of these phases adds up to the ~ 8 inch difference.
The growth of girls with TS not treated for their short stature has been studied sufficiently that TS-specific growth curves have been created and are available. Some bones grow even more slowly than others. The lower jaw bone may be quite small and contribute to orthodontic issues. The bones in the hands and wrist may be particularly affected, and some girls have small knuckles (due to short metacarpal bones). A few have bowing of the forearm and deformity of the wrist (Madelung deformity). There may also be changes in the knees which give a knocked-knee appearance, and in rare patients the hip(s) can be dislocated at birth or the top of the hip bone can slip off the long-bone during later years of growth (slipped capital femoral epiphysis). Finally the bones of the spine may grow in a curved fashion resulting in spinal curvature called scoliosis.
While girls with Turner syndrome do not lack pituitary growth hormone (GH), it has been shown in clinical studies that giving growth hormone can overcome some of the height deficit. The average height gain is about 4 inches (10 cm) or half of the deficit, with early institution of GH associated with greater growth and taller final height. GH is given by injection, and usually started in the preschool or early school years (unless diagnosis is delayed) since catch-up growth takes time. Once started, treatment usually continues so that growth can continue faster than if not treated, and isn鈥檛 stopped until final heightis reached (growing end of bones fuse, called 鈥渇used epiphyses鈥? or the girl and her family are satisfied with height reached. The majority of TS girls will also need estrogen therapy, and its timing is somewhat related to how much growth deficit is remaining at the time feminization is desirable. Estrogen contributes much less to a growth spurt in girls with TS than it does in girls without TS. On the other hand, it is the hormone that is responsible for the bones fusing. Thus, pediatric endocrinologists, who generally supervise growth hormone treatment, balance the need for feminization with the inches that can still be achieved before the bones fuse. The earlier growth hormone is started, and the taller the girl is, the earlier in adolescence that estrogen can be started without a negative effect on final height.
This article was contributed by Dr. Barbara Lippe, Member of the TSSUS Board of Directors.
Posted December, 2005
FERTILITY/ENDOCRINE ISSUES IN TURNER SYNDROME (TS)
Most women with TS have ovarian failure. In other words, they do not have ovaries capable of producing female hormones and eggs. They need hormonal treatment in order to undergo pubertal development and to have menstrual periods. Their reproductive organs are otherwise normal. They are able to have normal sexual relations. Generally, the only way to overcome infertility in TS is adoption or egg donation (embryo donation is also possible). In most women with TS the uterus responds well to hormonal preparation and it is capable of carrying a pregnancy normally. Before contemplating pregnancy, women with TS need to undergo a complete medical evaluation, with particular attention to the cardiovascular and renal systems. Pregnancy in women with TSshould be followed by a high-risk obstetrician.
This article was contributed by Dr. Luis Rodriguez, Member of the Medical Advisory Board.
Posted December, 2005
EAR AND HEARING DISORDERS IN TURNER SYNDROME
There are two common forms of hearing loss in Turner Syndrome. The first is conductive hearing loss caused by fluid behind the eardrum, which mostly affects younger girls with Turner Syndrome. This conductive loss is only a partial loss, but can still significantly affect hearing and communication. Consultation with an ear-nose-throat specialist is iimportant if the fluid persists or becomes infected frequently. There are a variety of options available to treatthis problem, including antibiotics and the placement of a tympanostomy tube in the eardrum. The conductive hearing loss generally will completely resolve if and when the fluid disappears.
The second type of hearing loss is sensorineural, caused by a primary problem in the inner ear (cochlea). This type of hearing loss is permanent, and often slowly progresses over years and decades. A few Turner Syndrome individuals have a partial sensorineural hearing loss as children. In contract, many Turner Syndrome women develop a partial sensorineural hearing loss primarily affecting the high pitches (frequencies) as adults. In most cases, hearing aids are an adequate method to rehabilitate sensorineural hearing loss since it does not typically progress to total or profound hearing loss.
This article was provided by Dr. Andrew Griffith, Member of the Medical Advisory Board.
Posted December, 2005 |
