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Thyroid nodules
What is the thyroid?
The normal thyroid is a butterfly shaped gland that lies at the base of the neck, in front of the windpipe. It
produces hormones that are important for the body's metabolism and organ function. Thyroid hormone
influences conditions such as heart rate, cholesterol level, muscle strength, skin condition, menstrual cycle
and mental state.
What is a thyroid nodule?
A nodule is a small lump, or localised growth in part of the thyroid gland. It differs from a goitre, which is a
generally enlarged thyroid gland. However, an enlarged thyroid gland (goitre) may contain one or more
nodules. A nodule differs from the surrounding thyroid tissue as it is usually raised or of a different
texture. Nodules are very common. Most thyroid nodules are not cancers, but any palpable nodule should
be evaluated. These growths may be fluid filled (cysts) or solid and formed of thyroid tissue. Sometimes
they can bleed into themselves and enlarge rapidly over several hours. The size of the nodules can vary
from a few millimetres to several centimetres. Thyroid nodules may be a sign of an underlying problem in
the thyroid gland and the cause should be investigated.
What causes a nodule?
About 95% of all nodules are due to benign conditions but a few are due to thyroid cancer. Benign causes
of a thyroid nodule include a cyst (collection of fluid), overactive thyroid tissue (toxic nodule), a benign
overgrowth of thyroid tissue called an adenoma, or many growths in an enlarged thyroid gland
(multinodular goitre).
Certain forms of radiation have been associated with an increased risk of cancerous nodules in the thyroid,
but only when the dose has been very high. Radiation at Chernobyl has been associated with an increased
risk of thyroid nodules and cancer. Regular X-rays are not a known risk factor but radiation therapy to the
neck, for example for another cancer, slightly increases the risk of thyroid cancer.
What are the symptoms of a thyroid nodule?
Usually there are no symptoms, but a person or their doctor may notice the lump incidentally. Sometimes
there may be a sensation of a lump in the throat and occasionally, difficulty swallowing, a cough or hoarse
voice. A toxic or overactive nodule may cause hyperthyroidism with symptoms of tremor, sweating, heat
intolerance and weight loss. Sometimes a nodule is found in an underactive thyroid gland (called
hypothyroidism). Symptoms of hypothyroidism include fatigue, feeling the cold, constipation and mild
weight gain.
How common are thyroid nodules?
Very common! Using sensitive ultrasound scanning about 50% of people have been shown to have a thyroid
nodule. But only about 5% of the population have a nodule that can be easily felt. Females are affected
more than males and nodules are more frequent in older people.
HealthInfo reference: 70795
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Issued: 22 July 2014
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Thyroid nodules
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How is a thyroid nodule diagnosed?
Initially your doctor will ask about your symptoms and medical history, and then examine you. Your doctor
may be able to distinguish nodules by carefully feeling the thyroid gland. A blood test to check the activity
of the thyroid gland will usually be done and often a scan of the thyroid is performed. This may be with
ultrasound or a special thyroid scan using a small amount of a radioactive substance that tells if the nodule
is overactive (a hot nodule) or inactive (a cold nodule). These tests are not dangerous or painful. The most
accurate test is a fine needle aspirate (FNA). This involves removing several small tissue samples from the
thyroid nodule with a thin needle. Local anaesthetic is usually used but you will still feel slight discomfort
from the needle. The tissue samples are then examined under the microscope looking for any cells
suspicious of a cancer.
How is a nodule treated?
The treatment for any thyroid nodule depends upon the cause. If the fine needle aspirate from the nodule
shows benign, non-cancerous cells, then the nodule may just be observed to make sure it does not grow
any larger. Sometimes thyroid hormone tablets are given to try and prevent other nodules forming but this
is rarely successful. If the nodule grows larger then a repeat needle test may be necessary. Occasionally the
needle test is inconclusive and needs to be repeated. If a second test is still not helpful then you may be
advised to have the nodule removed surgically.
If your thyroid nodule is overactive or toxic, then your doctor may recommend that you have either surgery
or radioiodine to destroy the overactive nodule. Sometimes drugs to reduce the level of thyroid hormone in
the blood are given before these treatments. If the nodule is cystic then the fluid may be removed with a
fine needle. If the cyst reforms, then surgery may be necessary.
What if my nodule is cancer?
In the rare case that your nodule is a cancer, most often it is curable. If the needle test is suspicious for
cancer, then surgical removal is recommended. It is very important that an experienced thyroid surgeon
does the operation. Thyroid surgery usually involves a few days in hospital and results in a scar at the base
of the neck. Complications of the surgery are rare (less than 2%) but include possible damage to the body's
calcium balance and vocal cords. Surgery is the main treatment to remove cancer. After surgery, radioactive
iodine may be given to destroy any remaining thyroid tissue. You will also be given thyroid hormone tablets
to replace the hormones made by your thyroid gland and to suppress the growth of cancer cells in any
remaining thyroid tissue. You will be followed closely with blood tests and sometimes further radioiodine
scans. Some forms of thyroid cancer run in families and if this type is found, then your family may need to
be checked. Remember that most patients with thyroid cancer have an excellent prognosis.
Do you still have any questions? Then please ask the doctor who sees you.
More information
If you wish to obtain more information, recommended web pages include:
National Institutes of Health (www.nlm.nih.gov/medlineplus)
The American Thyroid Association (www.thyroid.org)
Written by the Department of Endocrinology, Christchurch Hospital.Endorsed by HealthInfo clinical advisers.
Reviewed September 2013.
70795
HealthInfo reference: 70795

Issued: 22 July 2014
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Page 2 of 2