Basic Thyroid Information
What is the thyroid?
The thyroid is a small, butterfly-shaped gland just below the Adam's apple. This gland plays a very important role in controlling the body's metabolism, that is, how the body functions. It does this by producing thyroid hormones (T4 and T3), hormones that travel through the blood to every part of the body. Thyroid hormones tell the body how fast to work and use energy.
The thyroid gland works like an air conditioner. If there are enough thyroid hormones in the blood, the gland stops making the hormones (just as an air conditioner cycles off when there is enough cool air in a house). When the body needs more thyroid hormones, the gland starts producing again. The pituitary gland works like a thermostat, telling the thyroid when to start and stop. The pituitary sends thyroid stimulating hormone (TSH) to the thyroid to tell the gland what to do.
About 20 million Americans have some form of thyroid disease. The thyroid gland might produce too much hormone (hyperthyroidism), making the body use energy faster than it should, or too little hormone (hypothyroidism), making the body use energy slower than it should. The gland may also become inflamed (thyroiditis) or enlarged (goiter), or develop one or more lumps (nodules).
Who has thyroid disease?
- An estimated 20 million Americans have thyroid disorders, but more than half still remain undiagnosed.
- Approximately 1 out of every 8 women will develop a thyroid disorder in her lifetime.
- Women are 5 to 8 times more likely than men to suffer from a thyroid condition.
- The elderly are also more likely to suffer from hypothyroidism. By age 60, as many as 17 percent of women have an underactive thyroid.
- Five to 8 percent of women develop thyroid abnormalities after delivery of a child.
What is hyperthyroidism?
Hyperthyroidism makes the body speed up. It occurs when there is too much thyroid hormone in the blood ("hyper" means "too much"). Nearly 10 times more frequent in women, it affects about 2% of all women in the United States. The most common form of hyperthyroidism, Graves' disease, is caused by problems with the immune system and tends to run in families. It affects at least 2.5 million Americans, including Olympic athlete Gail Devers who won a gold medal in track after being diagnosed with and treated for Graves' disease. Symptoms include:
- fast heart rate
- increased perspiration
- muscle weakness
- trembling hands
- weight loss
- hair loss
- skin changes
- increased frequency of bowel movements
- decreased menstrual flow and less frequent menstrual flow
What is hypothyroidism?
Hypothyroidism causes the body to slow down. It occurs when there is too little thyroid hormone in the blood ("hypo" means "not enough"). Hypothyroidism affects more than 5 million people, many of whom don't know they have the disease. Women are more likely than men to have hypothyroidism.
- feeling slow or tired
- feeling cold
- drowsy during the day, even after sleeping all night
- slow heart rate
- poor memory
- difficulty concentrating
- muscle cramps
- weight gain
- husky voice
- thinning hair
- dry and coarse skin
- feeling depressed
- heavy menstrual flow
- milky discharge from the breasts
Many of the symptoms of hypothyroidism can occur normally with aging, so if you have one or two of them, there is probably no reason to worry. However, if you are concerned about any of these symptoms, you should see your doctor.
What is thyroiditis?
Thyroiditis is an inflammation of the thyroid gland and the most common cause of hypothyroidism. When patients with thyroiditis have any symptoms, they are usually the symptoms of hypothyroidism. It is also common to have an enlarged thyroid that may shrink over time. The type of thyroiditis seen most often is Hashimoto's thyroiditis, a painless disease of the immune system that runs in families. Hashimoto's thyroiditis affects about 5% of the adult population, increasing particularly in women as they age. Another form of thyroiditis affects women of childbearing age. Postpartum thyroiditis occurs in 5%-9% of women soon after giving birth and is usually a temporary condition.
What is a goiter?
A goiter is an abnormal swelling in the neck caused by an enlarged thyroid gland. It can become quite large. The problem occurs in at least 5% of the population worldwide. The most common cause of a goiter is lack of iodine, a chemical which the thyroid uses to produce its hormones. About 100 million people don't get enough iodine in their diets, but the problem has been solved in North America and Western Europe by adding iodine to salt. Even with the right amount of iodine, the thyroid gland can swell, creating a goiter. This can occur in any type of thyroid disease, including hyperthyroidism, hypothyroidism, thyroiditis, and thyroid cancer. However, many goiters develop with normal thyroid hormone levels and do not require treatment.
What are hot and cold nodules?
Thyroid nodules do not function like normal thyroid tissue. A thyroid image (scan) done with a radioactive chemical shows the size, shape, and function of the gland and of thyroid nodules. A nodule that takes up more of the radioactive material than the rest of the gland is called a hot nodule. A nodule that takes up less radioactive material is a cold nodule. Hot nodules are seldom cancerous, but less than 10% of all nodules are hot. Cold nodules may or may not be cancerous. All lumps in your neck should be checked by your doctor.