- The Thyroid
- What Is Cancer?
- Risk Factors
- Recognizing Symptoms
- Orthodox Treatment
- Side Effects of Treatment
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 voice box (larynx). It has two parts,
or lobes. The two lobes are separated by a thin section called
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 shellfish
and iodized salt.
What Is Cancer?
Cancer is a group of many related diseases. All cancers begin
in cells, the body's basic unit of life. Cells make up tissues,
and tissues make up the organs of the body.
Normally, cells grow and divide to form new cells as the
body needs them. When cells grow old and die, new cells take
Sometimes this orderly process goes wrong. New cells form
when the body does not need them, and old cells do not die
when they should. These extra cells can form a mass of tissue
called a growth or tumor. Growths on the thyroid are usually
Thyroid nodules can be benign or malignant:
Benign nodules are not cancer. Cells from benign nodules
do not spread to other parts of the body. They are usually
not a threat to life. Most thyroid nodules (more than 90 percent)
Malignant nodules are cancer. They are generally more serious
and may sometimes be life threatening. Cancer cells can invade
and damage nearby tissues and organs. Also, cancer cells can
break away from a malignant nodule and enter the bloodstream
or the lymphatic system. That is how cancer spreads from the
original cancer (primary tumor) to form new tumors in other
organs. The spread of cancer is called metastasis.
The following are the major types of thyroid cancer:
Papillary and follicular thyroid cancers account for
80 to 90 percent of all thyroid cancers. Both types 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 accounts for 5 to 10 percent
of thyroid cancer cases. It arises 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
Anaplastic thyroid cancer is the least common type
of thyroid cancer (only 1 to 2 percent of cases). It arises
in the follicular cells. The cancer cells are highly abnormal
and difficult to recognize. This type of cancer is usually
very hard to control because the cancer cells tend to grow
and spread very quickly.
If thyroid cancer spreads (metastasizes) outside the thyroid,
cancer cells are often found in nearby lymph nodes, nerves,
or blood vessels. If the cancer has reached these lymph nodes,
cancer cells may have also spread to other lymph nodes or
to other organs, such as the lungs or bones.
When cancer spreads from its original place to another part
of the body, the new tumor has the same kind of abnormal cells
and the same name as the primary tumor. For example, if thyroid
cancer spreads to the lungs, the cancer cells in the lungs
are thyroid cancer cells. The disease is metastatic thyroid
cancer, not lung cancer. It is treated as thyroid cancer,
not as lung cancer. Doctors sometimes call the new tumor "distant"
or metastatic disease.
No one knows the exact causes of thyroid cancer. Doctors
can seldom explain why one person gets this disease and another
does not. However, it is clear that thyroid cancer is not
contagious. No one can "catch" cancer from another
Research has shown that people with certain risk factors
are more likely than others to develop thyroid cancer. A risk
factor is anything that increases a person's chance of developing
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.
- Family history. Medullary thyroid cancer can be caused
by a change, or alteration, in a gene called RET. The altered
RET gene can be passed from parent to child. Nearly everyone
with the altered RET gene will develop medullary thyroid
- Being female. 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. People with anaplastic thyroid cancer are usually
more than 65 years old.
- Race. White people are more likely than Africans to be
diagnosed with thyroid cancer.
- Not enough iodine in the diet. The thyroid needs iodine
to make thyroid hormone. Iodine is always added to salt
to protect people from thyroid problems. Thyroid cancer
seems to be less common in countries where iodine is part
of the diet than in those where not.
Most people who have known risk factors do not get thyroid
cancer. On the other hand, many who do get the disease have
none of these risk factors. People who think they may be at
risk for thyroid cancer should discuss this concern with their
Early thyroid cancer often does not cause symptoms. But as
the cancer grows, symptoms may include:
- A lump, or nodule, in the front of the neck near the Adam's
- Hoarseness or difficulty speaking in a normal voice;
- Swollen lymph nodes, especially in the neck;
- Difficulty swallowing or breathing; or
- Pain in the throat or neck.
These symptoms are not sure signs of thyroid cancer. An infection,
a benign goiter, or another problem also could cause these
symptoms. Anyone with these symptoms should see a doctor as
soon as possible. Only a doctor can diagnose and treat the
If a person has symptoms that suggest thyroid cancer, the
doctor may perform a physical exam and ask about the patient's
personal and family medical history. The doctor also may order
laboratory tests and imaging tests to produce pictures of
the thyroid and other areas.
The exams and tests may include the following:
Physical exam -- The doctor will feel the neck, thyroid,
voice box, and lymph nodes in the neck for unusual growths
(nodules) or swelling.
Blood tests -- The doctor may test for abnormal levels
(too low or too high) of thyroid-stimulating hormone (TSH)
in the blood. TSH is made by the pituitary gland in the brain.
It stimulates the release of thyroid hormone. TSH also controls
how fast thyroid follicular cells grow.
If medullary thyroid cancer is suspected, the doctor may
check for abnormally high levels of calcium in the blood.
The doctor also may order blood tests to detect an altered
RET gene or to look for a high level of calcitonin.
Ultrasonography -- The ultrasound device uses sound
waves that people cannot hear. The waves bounce off the thyroid,
and a computer uses the echoes to create a picture called
a sonogram. From the picture, the doctor can see how many
nodules are present, how big they are, and whether they are
solid or filled with fluid.
Radionuclide scanning -- The doctor may order a nuclear
medicine scan that uses a very small amount of radioactive
material to make thyroid nodules show up on a picture. Nodules
that absorb less radioactive material than the surrounding
thyroid tissue are called cold nodules. Cold nodules may be
benign or malignant. Hot nodules take up more radioactive
material than surrounding thyroid tissue and are usually benign.
Biopsy -- The removal of tissue to look for cancer
cells is called a biopsy. A biopsy can show cancer, tissue
changes that may lead to cancer, and other conditions. A biopsy
is the only sure way to know whether a nodule is cancerous.
The doctor may remove tissue through a needle or during surgery:
Fine-needle aspiration: For most patients, the doctor
removes a sample of tissue from a thyroid nodule with a thin
needle. A pathologist looks at the cells under a microscope
to check for cancer. Sometimes, the doctor uses an ultrasound
device to guide the needle through the nodule.
Surgical biopsy: If a diagnosis cannot be made from
the fine-needle aspiration, the doctor may operate to remove
the nodule. A pathologist then checks the tissue for cancer
If the diagnosis is thyroid cancer, the doctor needs to know
the stage, or extent, of the disease to plan the best treatment.
Staging is a careful attempt to learn whether the cancer has
spread and, if so, to what parts of the body.
The doctor may use ultrasonography, magnetic resonance imaging
(MRI), or computed tomography (CT) to find out whether the
cancer has spread to the lymph nodes or other areas within
the neck. The doctor may use a nuclear medicine scan of the
entire body, such as a radionuclide scan known as the "diagnostic
I-131 whole body scan," or other imaging tests to learn
whether thyroid cancer has spread to distant sites.
People with thyroid cancer have many treatment options. Depending
on the type and stage, thyroid cancer may be treated with
surgery, radioactive iodine, hormone treatment, external radiation,
or chemotherapy. Some patients receive a combination of treatments.
Surgery is the most common treatment for thyroid cancer.
The surgeon may remove all or part of the thyroid. The type
of surgery depends on the type and stage of thyroid cancer,
the size of the nodule, and the patient's age.
Total thyroidectomy -- Surgery to remove the entire thyroid
is called a total thyroidectomy. The surgeon removes the thyroid
through an incision in the neck. Nearby lymph nodes are sometimes
removed, too. If the pathologist finds cancer cells in the
lymph nodes, it means that the disease could spread to other
parts of the body. In a small number of cases, the surgeon
removes other tissues in the neck that have been affected
by the cancer. Some patients who have a total thyroidectomy
also receive radioactive iodine or external radiation therapy.
Lobectomy -- Some patients with papillary or follicular thyroid
cancer may be treated with lobectomy. The lobe with the cancerous
nodule is removed. The surgeon also may remove part of the
remaining thyroid tissue or nearby lymph nodes. Some patients
who have a lobectomy receive radioactive iodine therapy or
additional surgery to remove remaining thyroid tissue.
Nearly all patients who have part or all of the thyroid removed
will take thyroid hormone pills to replace the natural hormone.
After the initial surgery, the doctor may need to operate
on the neck again for thyroid cancer that has spread. Patients
who have this surgery also may receive I-131 therapy or external
radiation therapy to treat thyroid cancer that has spread.
Radioactive iodine therapy (also called radioiodine
therapy) uses radioactive iodine (I-131) to destroy thyroid
cancer cells anywhere in the body. The therapy usually is
given by mouth (liquid or capsules) in a small dose that causes
no problems for people who are allergic to iodine. The intestine
absorbs the I-131, which flows through the bloodstream and
collects in thyroid cells. Thyroid cancer cells remaining
in the neck and those that have spread to other parts of the
body are killed when they absorb I-131.
If the dose of I-131 is low enough, the patient usually receives
I-131 as an outpatient. If the dose is high, the doctor may
protect others from radiation exposure by isolating the patient
in the hospital during the treatment. Most radiation is gone
in a few days. Within 3 weeks, only traces of radioactive
iodine remain in the body.
Patients with medullary thyroid cancer or anaplastic thyroid
cancer generally do not receive I-131 treatment. These types
of thyroid cancer rarely respond to I-131 therapy.
Hormone treatment after surgery is usually part of
the treatment plan for papillary and follicular cancer. When
a patient takes thyroid hormone pills, the growth of any remaining
thyroid cancer cells slows down, which lowers the chance that
the disease will return.
After surgery or I-131 therapy (which removes or destroys
thyroid tissue), people with thyroid cancer may need to take
thyroid hormone pills to replace the natural thyroid hormone.
External radiation therapy (also called radiotherapy)
uses high-energy rays to kill cancer cells. A large machine
directs radiation at the neck or at parts of the body where
the cancer has spread.
External radiation therapy is local therapy. It affects cancer
cells only in the treated area. External radiation therapy
is used mainly to treat people with advanced thyroid cancer
that does not respond to radioactive iodine therapy. For external
radiation therapy, patients go to the hospital or clinic,
usually 5 days a week for several weeks. External radiation
may also be used to relieve pain or other problems.
Chemotherapy, the use of drugs to kill cancer cells,
is sometimes used to treat thyroid cancer. Chemotherapy is
known as systemic therapy because the drugs enter the bloodstream
and travel throughout the body. For some patients, chemotherapy
may be combined with external radiation therapy.
Side Effects of Orthodox Treatment
Because cancer treatment may damage healthy cells and tissues,
unwanted side effects sometimes occur. These side effects
depend on many factors, including the type and extent of the
treatment. Side effects may not be the same for each person,
and they may even change from one treatment session to the
next. Before treatment starts, the health care team will explain
possible side effects and suggest ways to help the patient
Patients are often uncomfortable for the first few days after
surgery. However, medicine can usually control their pain.
Patients should feel free to discuss pain relief with the
doctor or nurse. It is also common for patients to feel tired
or weak. The length of time it takes to recover from an operation
varies for each patient.
After surgery to remove the thyroid and nearby tissues or
organs, such as the parathyroid glands, patients may need
to take medicine (thyroid hormone) or vitamin and mineral
supplements (vitamin D and calcium) to replace the lost functions
of these organs. In a few cases, certain nerves or muscles
may be damaged or removed during surgery. If this happens,
the patient may have voice problems or one shoulder may be
lower than the other.
Radioactive Iodine (I-131) Therapy
Some patients have nausea and vomiting on the first day of
I-131 therapy. Thyroid tissue remaining in the neck after
surgery may become swollen and painful. If the thyroid cancer
has spread to other parts of the body, the I-131 that collects
there may cause pain and swelling.
Patients also may have a dry mouth or lose their sense of
taste or smell for a short time after I-131 therapy. Chewing
sugar-free gum or sucking on sugar-free hard candy may help.
During treatment, patients are encouraged to drink lots of
water and other fluids. Because fluids help I-131 pass out
of the body more quickly, the bladder's exposure to I-131
Because radioactive iodine therapy destroys the cells that
make thyroid hormone, patients may need to take thyroid hormone
pills to replace the natural hormone.
A rare side effect in men who received large doses of I-131
is loss of fertility. In women, I-131 may not cause loss of
fertility, but some doctors suggest that women avoid pregnancy
for one year after I-131 therapy.
Researchers have reported that a very small number of patients
may develop leukemia years after treatment with high doses
Thyroid hormone pills seldom cause side effects. However,
a few patients may get a rash or lose some of their hair during
the first months of treatment.
The doctor will closely monitor the level of thyroid hormone
in the blood during followup visits. Too much thyroid hormone
may cause patients to lose weight and to feel hot and sweaty.
It also may cause chest pain, cramps, and diarrhea. (The doctor
may call this condition "hyperthyroidism.") If the
thyroid hormone level is too low, the patient may gain weight,
feel cold, and have dry skin and hair. (The doctor may call
this condition "hypothyroidism.") If necessary,
the doctor will adjust the dose so that the patient takes
the right amount.
External Radiation Therapy
External radiation therapy may cause patients to become very
tired as treatment continues. Resting is important, but doctors
usually advise patients to try to stay as active as they can.
In addition, when patients receive external radiation therapy,
it is common for their skin to become red, dry, and tender
in the treated area. When the neck is treated with external
radiation therapy, patients may feel hoarse or have trouble
swallowing. Other side effects depend on the area of the body
that is treated. If chemotherapy is given at the same time,
the side effects may worsen. The doctor can suggest ways to
ease these problems.
The side effects of chemotherapy depend mainly on the specific
drugs that are used. The most common side effects include
nausea and vomiting, mouth sores, loss of appetite, and hair
loss. Some side effects may be relieved with medicine.