What Is It?
Thyroid cancer is the uncontrolled growth of abnormal cells in the thyroid gland. The thyroid gland is shaped like a butterfly. It is located under the Adam's apple in the front of the neck. Most cases of thyroid cancer can be cured.
One of the functions of the thyroid gland is to make thyroid hormone, which requires iodine. The gland collects iodine from foods, concentrates it, and produces thyroid hormone. Doctors often exploit this important function when treating thyroid cancer.
Thyroid hormone helps regulate the body's metabolism and energy level. An overactive thyroid can lead to hyperactivity, the "jitters," and an irregular heart rhythm; an underactive thyroid, fatigue and sluggishness. Cancer can affect the thyroid and cause these changes.
Nestled against the thyroid gland are four very small glands called parathyroid glands. They play a role in regulating the body's use of calcium. The nerve that controls the voice box is also very close to the thyroid. If you need a thyroid operation, your surgeon needs to identify and avoid damaging these structures. If the voice box nerve is damaged, for example, your voice may sound hoarse permanently.
The thyroid has two types of cells. They produce hormones that help regulate body functions:
There are five types of thyroid cancers:
Rarely, tumors arising from connective tissue (sarcomas) and lymph nodes (lymphomas) can start in the thyroid gland. They are treated differently than other thyroid cancers.
Although scientists have not identified the exact cause of thyroid cancer, some studies have shown that people exposed to nuclear fallout or nuclear power plant accidents have a higher risk of developing thyroid cancer. In part, this is due to the presence of radioactive iodine. Because the thyroid has an attraction for iodine, the thyroid tissue accumulates this radioactive substance. Over time, it may cause cancer.
Others who have a higher risk of thyroid cancer include people who
Individuals who have received radiation therapy to the chest (to treat Hodgkin's disease, for example) have an increased incidence of thyroid abnormalities, including cancer. This is even more likely if the thyroid was included in the radiation field. Such people will need life-long follow up to assess thyroid function and check for cancer.
Some forms of thyroid cancer are inherited. These occur alone (inherited MTC) or as part of a familial cancer syndrome known as multiple endocrine neoplasia (MEN) type 2. Patients with MEN-2 develop tumors in other parts of the body, such as the adrenal gland and peripheral nervous system.
Some forms of thyroid cancer may be caused by genetic changes (mutations) that occur after birth.
Thyroid cancer is rare, accounting for only a small percentage of all cancers. However, it does strike more women than men.
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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.
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