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Thyroid Disease Overview

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Updated June 16, 2003

What is the thyroid and why should I worry about it?

The thyroid is a small gland in the neck, just under the Adam's apple. Shaped like a butterfly, the thyroid plays an important role in a person's health and affects every organ, tissue, and cell in the body.

It makes hormones that help to regulate the body's metabolism (how the body uses and stores energy from foods eaten) and organ functions. When the thyroid is not working properly (called thyroid disorder), it can affect your body weight, energy level, muscle strength, skin health, menstrual cycle (periods), memory, heart rate, and cholesterol level. Thyroid disorders happen: when the thyroid gland is not as active as it should be (called underactive thyroid) -- when the thyroid is more active than it should be (called overactive thyroid), or when the thyroid is enlarged (called goiter or nodule).

People with thyroid enlargement can have underactive, overactive or normal thyroid function. Thyroid disorders are much more common in women than in men. About 1 out of every 8 American women will develop a thyroid disorder. Underactive or overactive thyroid can be found with a blood test (called a thyroid stimulating hormone or TSH test), and is most often treated with medication and sometimes surgery or radioactive iodine.

What are the different types of thyroid disorders?

Hypothyroidism (underactive thyroid)

This is the most common type of thyroid disorder, where the thyroid makes too little of the thyroid hormone that your body needs to function properly. It is most often caused by Hashimoto's disease. With this disease, the body's immune system (which normally protects you from disease) thinks the thyroid is a foreign invader and tries to destroy the thyroid. When damage is done to the thyroid, it can become larger (called goiter).

Not getting enough -- or getting too much -- iodine in a person's diet can also cause hypothyroidism. Not getting enough iodine is more common outside of the United States.

Being female, over 40 years of age, having a close family member with thyroid disease, and recently having had a baby are things that can increase the chance of getting hypothyroidism.

Hyperthyroidism (overactive thyroid)

When the thyroid gland is overactive, it makes too much of the thyroid hormone that your body needs to be healthy. This condition affects women more than men. In young women, hyperthyroidism is most often caused by Graves' disease. With this disease, the body's immune system tricks the thyroid into making too much thyroid hormone. The entire thyroid becomes enlarged and overactive. Older women may get another form of hyperthyroidism (toxic nodular goiter), where overactive thyroid cells group together and form a lump in the neck (called a thyroid nodule) that makes more of the thyroid hormone than the body needs. Some thyroid disorders initially cause overactive thyroid, but at a later point in time cause underactive thyroid, due to damage done to the thyroid gland.

Postpartum thyroiditis

After giving birth, a woman's thyroid can swell and become larger or inflamed. This can cause changing levels of thyroid hormone in the body. Sometimes high levels can be followed by low levels of thyroid hormone. After 6 months or less, this condition usually goes away with no permanent damage to the thyroid. While common, thyroid disorders after pregnancy are often hard to detect since some of the symptoms, such as having trouble sleeping, fatigue, depression, or weight change are viewed as normal when a woman has a new baby. The symptoms can also be mild. Usually only short-term treatment is required until the thyroid recovers normal function. Sometimes after pregnancy, a woman can get hypothyroidism (underactive thyroid), which persists and needs long-term treatment with medication.

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