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There are several types of thyroid cancer.

Women develop thyroid cancer more often than men.

Known genetic variants are associated with an increased risk of thyroid cancer.

If diagnosed early, treatment can be very effective.

The thyroid produces metabolism-regulating hormones

The thyroid gland is a butterfly-shaped gland located in the lower front of the neck, below the larynx (‘Adam’s apple’), that is part of the body´s hormone-producing endocrine system. The hormones produced by the thyroid gland help regulate metabolism, that is the rate at which the body burns energy. A thyroid gland that is not active enough in producing hormones can slow metabolism, resulting in weight-gain, fatigue, and increased sensitivity to cold temperatures. Too much hormone-production can lead to increased metabolism, resulting in weight-loss, increased heart rate and sensitivity to heat.

Thyroid cancer is the most common endocrine cancer

Thyroid cancer is the most common cancer of the endocrine system, its incidence in industrialized countries has been rising over the past few decades. In 2008, the estimated number of new cases in the U.S. was about 37,000 with a gender bias of about three females affected for each male. The average age at diagnosis is around 60 years for males and 47 years for females.

High cure-rate if diagnosed early

There are four main types of thyroid cancer. Those referred to as papillary and follicular types, account for over 90% of all thyroid cancers, while the rarer medullary and anaplastic types account for the remaining 10%. In general, thyroid cancer is one of the least deadly cancers. If diagnosed at an early stage, treatment is usually very effective and survival prospects are good.

Thyroid cancer has a strong genetic component

As is the case with most cancers, thyroid cancer is thought to be the result of both environmental and genetic factors. However, thyroid cancer has been estimated to have one of the strongest genetic components of all cancers, although to date, very few genetic variants have been discovered.

Common genetic variants contribute to an increased risk

Scientists at deCODE genetics have identified two genetic variants, on chromosomes 9 and 14, associated with increased risk of thyroid cancer. The variants contribute to an increased risk of the two main types of thyroid cancer, papillary and follicular. Furthermore, the risk alleles are associated with younger age at diagnosis.

deCODEme can calculate your genetic risk for thyroid cancer

The deCODEme Complete Scan and the deCODEme Cancer Scan identify these variants and provide an interpretation of the associated risk for the development of thyroid cancer for individuals of European descent. At this time risk information is not available for other ethnicities.

Known risk factors for thyroid cancer

There is still much to learn about the causes of thyroid cancer, however the following factors are known to contribute to and individual´s risk:

• Radiation exposure, including radiation in the form of repeated X-rays of the neck.
• Family history risk has been reported to be highest for first degree male relatives of male patients but lowest for first degree female relatives of female patients.
• Gender and age. For reasons that aren’t clear, women are two to three times more likely to develop thyroid cancer than men. Although thyroid cancers can occur in people of all ages, most cases of papillary and follicular thyroid cancer are found in people between the ages of 20 and 60 years.
• Ethnicity. Individuals of European, Asian and Pacific Islander ancestry are more likely to develop thyroid cancer than African Americans, American Indians or Hispanics.
• Certain inherited conditions for example familial adenomatous polyposis can increase the risk of papillary thyroid cancer.
• Iodine is an element found in seafood, some vegatables and in iodized salt, and has been identified by some studies as a possible risk factor for thyroid cancer. Follicular thyroid cancers are more common in areas of the world where people’s diets are low in iodine. This risk factor does not play a significant role where dietary iodine is plentiful. More studies are needed to determine the role of iodine a risk factor for thyroid cancer.

Knowing your genetic risk is important for prevention

Since thyroid cancer seems to have such a strong genetic basis, knowing your genetic risk and monitoring possible symptoms of thyroid cancer can be preventative in itself.

Avoiding radiation exposure is of course is always recommended, although current X-ray technology is such that the benefits almost always outweigh the risk.

Early thyroid cancer can have no apparent symptoms, or it can have symptoms associated with changes in thyroid hormone production (i.e. weight-loss or weight-gain, fatigue, change in heart-rate and heat sensitivity etc). Some patients with thyroid cancer become aware of a gradually enlarging lump in the front portion of the neck which usually moves with swallowing. Occasionally, the lump may cause a feeling of pressure, hoarseness or change of voice or trouble breathing or swallowing.

There are many reasons the thyroid gland might be larger than usual, and most of the time it is not cancer. Those who find an unusual lump in their neck should always bring this to the attention of their physician, even in the absence of other symptoms.

Fortunately, most types of thyroid cancer can be diagnosed early and cured completely. Treatment usually entails removing the suspected part of the thyroid gland and any abnormal lymph glands. If cancer is confirmed, radioactive iodine treatment is usually recommended in order to destroy any remaining malignant thyroid cells and to reduce the risk of cancer recurrence.

More information

• The American Cancer Society. What is Thyroid Cancer?
• Medline Plus – Trusted Health Information for You
• The National Cancer Institute

This content was last reviewed on February 23, 2011.

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