THYROID CANCER
Your thyroid is a butterfly-shaped gland in your neck,
just above your collarbone. It makes hormones that help
the body work normally. Anyone can get cancer of the
thyroid gland. But certain factors may increase the risk.
These include
• Being between ages 25 and 65
• Being a woman
• Being Asian
• Having a family member who has had thyroid disease
• Having radiation treatments to your head or neck
You should see a doctor if you have a lump or swelling
in your neck. Your doctor can order tests to see if you
have cancer and, if so, which type. Treatment depends
on the type and how far the cancer has spread. They include
surgery, radioactive iodine, hormone treatment, radiation
therapy or chemotherapy. Some patients receive a combination
of treatments.
Risk Factors
Doctors often cannot explain why one person develops
thyroid cancer and another does not. However, it is clear
that no one can catch thyroid cancer from another person.
Research has shown that people with certain risk factors
are more likely than others to develop thyroid cancer.
A risk factor is something that may increase the chance
of developing a disease.
Studies have found the following risk factors for thyroid
cancer:
People exposed to high levels of radiation
are much more likely than others to develop papillary
or follicular thyroid cancer. One important source of
radiation exposure is treatment with x-rays. 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.
(Routine diagnostic x-rays - such as dental x-rays
or chest x-rays - use very low doses of radiation. Their
benefits usually outweigh their risks. However, repeated
exposure could be harmful, so it's a good idea to talk
with your dentist and doctor about the need for each
x-ray and to ask about the use of shields to protect
other parts of the body.)
Another source of radiation is radioactive fallout.
This includes fallout from atomic weapons testing (such
as the testing in the United States and elsewhere in
the world, mainly in the 1950s and 1960s), nuclear power
plant accidents (such as the Chornobyl [also called Chernobyl]
accident in 1986), and releases from atomic weapons production
plants (such as the Hanford facility in Washington state
in the late 1940s). Such radioactive fallout contains
radioactive iodine (I-131) and other radioactive elements.
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 of thyroid diseases.
For example, children exposed to radioactive iodine from
the Chornobyl accident have an increased risk of thyroid
cancer.
For more information, you
may want to read the NCI fact sheet I-131 and Radioactive
Fallout: Questions and Answers. Information on how
to get NCI fact sheets is available in the "National Cancer Institute Publications" section.
• Family history of medullary thyroid cancer: Medullary
thyroid cancer sometimes runs in families. A change in
a gene called RET can be passed from parent to child.
Nearly everyone with the changed RET gene develops medullary
thyroid cancer. The disease occurs alone as familial
medullary thyroid cancer or with other cancers as multiple
endocrine neoplasia (MEN) syndrome.
A blood test can detect the changed RET gene. If it's
found in a person with medullary thyroid cancer, the
doctor may suggest that family members be tested. For
those who have the changed gene, the doctor may recommend
frequent lab tests or surgery to remove the thyroid before
cancer develops.
• Family history of goiters or colon growths: A small
number of people with a family history of having goiters
(swollen thyroids) with multiple thyroid nodules are
at risk for developing papillary thyroid cancer. Also,
a small number of people with a family history of having
multiple growths on the inside of the colon or rectum
(familial polyposis) are at risk for developing papillary
thyroid cancer.
• Personal history: People with
a goiter or benign thyroid nodules have an increased
risk of thyroid cancer.
• Being female: In the United States,
women are almost three times more likely than men to
develop thyroid cancer.
• Age over 45: Most people with
thyroid cancer are more than 45 years old. Most people
with anaplastic thyroid cancer are more than 60 years
old.
• Iodine: Iodine is a substance
found in shellfish and iodized salt. Scientists are studying
iodine as a possible risk factor for thyroid cancer.
Too little iodine in the diet may increase the risk of
follicular thyroid cancer. However, other studies show
that too much iodine in the diet may increase the risk
of papillary thyroid cancer. More studies are needed
to know whether iodine is a risk factor.
