Lee Chung Horn
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   THYROID DISORDERS

 

HYPOTHYROIDISM 

What is hypothyroidism?

A condition in which the thyroid gland, which is located in the neck, does not make sufficient thyroid hormone to meet the body's requirements. Hypothyroidism is often referred to as an "underactive thyroid gland".


What causes hypothyroidism?

Almost all hypothyroidism is caused by autoimmune disease. In this condition, which is called Hashimoto's thyroiditis or Hashimoto's disease, the immune system goes awry and begins to destroy the thyroid gland. This is a gradual process. It is not usually associated with thyroid gland discomfort, but may cause the gland to enlarge or shrink in size. The autoimmune disease is restricted to the thyroid gland; consequently, treatment with thyroid hormone (also known as L-thyroxine) completely corrects the condition.

Previous treatments for hyperthyroidism (an overactive thyroid gland) may also result in hypothyroidism. These treatments include radioactive iodine therapy or previous thyroid surgery. Patients who undergo total removal of thyroid gland for thyroid cancer will also develop hypothyroidism. Hypothyroidism may also arise from a inflammatory condition called de Quervain's thyroiditis.

How common is hypothyroidism?

Hypothyroidism is relatively common. It affects between 1 in 100 to 3 in 100 women of child-bearing age. It is more common in women than in men, and it becomes more common with age. Hypothyroidism occurs in up to 5 to 10 percent of older women.

What are the symptoms of hypothyroidism?

Hypothyroidism slows metabolism and affects essentially every system in the body. Symptoms include generalized fatigue, weight gain, thinning (brittle) hair, dry scaly skin, thin nails that break easily, constipation, alterations in menses, aching muscles, and slow heart rate. You may notice changes in behavior, such as decreased ability to concentrate, reading and calculating are more difficult, and you may experience decreased interest in personal relationships or work. Hypothyroidism can cause or worsen depression.

How is hypothyroidism tested?

A blood test is performed. It measures your thyroid hormone (thyroxine or T4) and TSH (Thyroid-stimulating hormone) levels.

How are the thyroid test results interpreted?

An elevation of TSH is a very sensitive index of reduced thyroid function. Somewhat like the thermostat in your home, when thyroid hormone levels fall, TSH (the furnace) is switched on to stimulate the thyroid gland. When thyroid hormone levels are low for a long time, TSH levels rise to a high level. Thus, hypothyroidism is characterized by a TSH level that is above the normal range and a thyroxine level that is below or at the low end of the normal range (everyone's set point is a little different). Your doctor can assist in the interpretation of these results, or you may wish to see a physician (an Endocrinologist) who specializes in hormonal disorders. A medication called L-Thyroxine (L-T4) is used to replace the missing thyroid hormone. It is chemically identical to those made by your own thyroid gland. Consequently, when the correct doses are prescribed and restore your metabolism to normal, the treatment is not accompanied by side effects.

L-thyroxine has to be taken long-term. Once it is discontinued or interrupted for a short time, your level of thyroid hormone may start to fall again. Long term thyroxine treatment is very safe--do not confuse it with HRT (HRT refers to female hormone replacement).

During pregnancy, patients with hypothyroidism often need to increase their dose of thyroxine. This is to ensure that the developing fetus gets adequate thyroid hormone. Your endocrinologist would help you to stay on the correct dose throughout your pregnancy.


 

Copyright of Lee Chung Horn Diabetes & Endocrinology 2009