Hypothyroidism

Hypothyroidism is the disease state caused by insufficient production of thyroid hormoneby the thyroid gland. There are several distinct causes for chronic hypothyroidism, the most common being Hashimoto's thyroiditisand hypothyroidism following radioiodinetherapy for hyperthyroidism.

The severity of hypothyroidism varies widely. Patients are classified as "subclinical hypothyroid" if diagnostic findings show thyroid hormone abnormalities, but they do not exhibit any symptoms. Others have moderate symptoms that can be mistaken for other diseases and states. Advanced hypothyroidism may cause severe complications, the most serious one of which is myxedema.

Signs and symptoms

Adults

• Slowed speechand a hoarse, breaking voice
• Impaired memory
• Increased sensitivity to heatand cold
• A slow heart rateand sluggish reflexes
• Dry puffy skin, especially on the face, and hair loss, especially thinning of the outer 1/3 of the eyebrows
• Depression(especially in the elderly)
• Weight gainand obesity
• Anemia
• Slowed metabolism
• Constipation
• Fatigue
• Choking sensationor difficulty swallowing
• Shortness of breath
• Increased need for sleep
• Muscle crampsand joint pain
• Decreased sex drive
• Brittle fingernails
• Paleness
• Irritability
• Abnormal menstrual cycles
• Thin, fragile or absent cuticles
• Infertilityor difficulty becoming pregnant
• Elevated serum cholesterol

Children

Very Early Infancy

• Feeding problems
• Constipation
• Hoarseness
• Excessive sleepiness

Later Infancy/Toddlerhood

• Protruding abdomen
• Rough, dry skin
• Delayed teething

After Toddlerhood

• Lack of normal growth
• Abnormally shortfor age on height/weight charts
• Puffy, bloated appearance
• Below-normal intelligencefor age

Causes

Neonatal hypothyroidism

Thyroid hormone is very important to neural development in the neonatal period. A deficiency of thyroid hormones can lead to cretinism. For this reason it is important to detect and treat thyroid deficiency early. In Australia, the Netherlands, and many other countries this is done by testing for TSHon the routine neonatal heel pricksperformed by law on all newborn babies.

Hashimoto's thyroiditis

Sometimes called Hashimoto's Disease, this is part of the spectrum of autoimmune diseasesand is related to Graves' disease, lymphocyticthyroiditis, and other organ-related autoimmune conditions such as Addison's disease, diabetes, premature menopauseand vitiligo. Hashimoto's is a lymphocytic and plasmacytic thyroid inflammationthat eventually destroys the thyroid. Patients require permanent thyroid hormone replacement.

Pituitary failure

Reduction or loss of TSH secretion by the pituitaryis a rare cause of hypothyroidism. This constellation is usually referred to as "secondary hypothyroidism". Even rarer is tertiary hypothyroidism that is caused either by hypothalamic lesions or by interruption of signal transfer in the portal veins connecting the hypothalamusto the pituitary gland (Pickardt syndrome).

Iatrogenic

Hypothyroidism may occur as an adverse reaction to lithiumused in the treatment of mood disorders, and in response to interferonand IL-2treatment (e.g. for cancer). It may also be a result of the antiarrhythmic amiodarone.

Iodine deficiency

Severe iodine deficiency is another major cause of hypothyroidism. In areas of the world where there is an iodine deficiency in the diet, severe hypothyroidism can be seen in 5 to 15% of the population. In many countries, iodine deficiency is very rare due to the small amount of iodine salt that is added to common table salt.

Surgery on the thyroid is generally done in a form that allows some hormone-producing tissue to remain. Nevertheless, some patients will need hormone supplementation after surgery.

Treatment

• Substitution of thyroid hormones by taking thyroxine(T4) tablets, usually in the form of levothyroxine. Doses are started with smaller amounts of thyroxine and then slowly titrated under control of TSH levels. Usually the maintenance dose is about 1 to 2 micrograms (µg) per kilogram of body weight.

• During the 1950s synthetic thyroxine became available and gradually replaced the long used Armour Thyroid which is created from dessicated pig thyroid glands and contains a ratio of three parts T4 to one part T3. These drugs were never FDA tested and grandfathered in. In the late 90s when the FDA did require them to be tested many of them failed and there is much controversy over their approval. One big problem is that many of them were initially tested on male medical students and females typically have a very different response due to poor T3 conversion (your body converts T4 into T3). T3 is the active form of thyroxine and several organs including the liver, kidneys and brain require T3 directly to function. Proponents of the synthetics argue that the liver converts T4 to T3 naturally however most of these tests were done in men and often women and many others show poor conversion rates. Proponents for the new synthetics argued they were more stable although this was never proven nor tested. Worse, administering T4 to a patient who is having conversion problems can actually block the use and absorption of available T3. Patients who do not respond to a T4 based product such as Levoxyl are switched to a T3 containing regimen such as Armour Thyroid and show imporvement. Since T3 rapidly breaks down in the blood stream another strategy is to take Armour Thyroid in divided doses 4 times a day or to add Cytomel(synthetic T3) in a fractional dose throughout the day (often 10mg suffices, broken into 4 pieces). Supplementing with T3 is very effective in overweight patients as T3 further breaks down into T2 which has been shown to be essential in fat metabolism and T2 is often taken by body builders to loose fat.

• Deficiencies of some dietary mineralsand iodinecan lead to hypothyroidism. Supplementation can be an effective treatment, but only if iodine deficiency has been documented, which is very rare in the Western world.

See also

• hyperthyroidism
• thyroxine

External link

• DMOZ
• Hypothyroidism Primer
• Network for Sustained Elimination of Iodine Deficiencybg:???????????????

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This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Hypothyroidism Wikipedia article Hypothyroidism.