Thyroid Cancer

 The thyroid is a gland in the neck. It has two kinds of cells that make hormones. Follicular cells make thyroid hormone, which affects heart rate, body temperature, and energy level. C cells make calcitonin, a hormone that helps control the level of calcium in the blood.

 The thyroid is shaped like a butterfly and lies at the front of the neck, beneath the larynx. It has two parts, or lobes. The two lobes are separated by a thin section called the isthmus.

 A healthy thyroid is a little larger than a quarter. It usually cannot be felt through the skin. A swollen lobe might look or feel like a lump in the front of the neck. A swollen thyroid is called a goiter. Most goiters are caused by not enough iodine in the diet. Iodine is a substance found in iodized salt.

The thyroid cancer is the cancer that forms in the thyroid gland. The three main types of thyroid cancer are papillary, follicular, medullary thyroid cancer. The three types are based on how the cancer cells look under a microscope.

- Papillary and follicular thyroid cancers begin in the follicular cells of the thyroid. Most papillary and follicular thyroid cancers tend to grow slowly. If they are detected early, most can be treated successfully.

- Medullary thyroid cancer begins in C cells, not follicular cells. Medullary thyroid cancer is easier to control if it is found and treated before it spreads to other parts of the body.

Risk Factors

The following risk factors are associated with an increased chance of developing thyroid cancer:

 Radiation. People exposed to high levels of radiation are much more likely than others to develop papillary or follicular thyroid cancer.

Between the 1920s and the 1950s, doctors used high-dose x-rays to treat children who had enlarged tonsils, acne, and other problems affecting the head and neck. Later, scientists found that some people who had received this kind of treatment developed thyroid cancer. (diagnostic x-rays -- such as dental x-rays or chest x-rays -- use very small doses of radiation. Their benefits nearly always outweigh their risks. However, repeated exposure could be harmful, so it is a good idea for people to talk with their dentist and doctor about the need for each x-ray.)

 Another source of radiation is radioactive fallout. This includes fallout from atomic weapons testing, nuclear power plant accidents and releases from atomic weapons production plants. Such radioactive fallout contains radioactive iodine (I-131). People who were exposed to one or more sources of I-131, especially if they were children at the time of their exposure, may have an increased risk for thyroid diseases.

 Females. In the United States, women are two to three times more likely than men to develop thyroid cancer.

 Age. Most patients with thyroid cancer are more than 40 years old.

 Race. In the United States, white people are more likely than African Americans to be diagnosed with thyroid cancer.

 Not enough iodine in the diet. The thyroid needs iodine to make thyroid hormone. In the United States, iodine is added to salt to protect people from thyroid problems. Thyroid cancer seems to be less common in the United States than in countries where iodine is not part of the diet.

Symptoms

Early thyroid cancer often does not cause symptoms. But as the cancer grows, symptoms may include:

- A lump in the front of the neck near the Adam's apple;

- difficulty speaking in a normal voice;

- Swollen lymph nodes, especially in the neck;

- Difficulty swallowing or breathing;

- Pain in the throat.