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What is the thyroid gland?
The thyroid is a gland that makes and stores essential hormones that help regulate the heart rate, blood pressure, body temperature, and the rate of chemical reactions (metabolism) in the body. It is located in the anterior neck just below the "Adam's apple."
The thyroid gland is the main part of the body that takes up iodine. In a thyroid scan, iodine is labeled with a radioactive tracer, and a special camera is used to measure how much tracer is absorbed from the bloodstream by the thyroid gland. If a patient is allergic to iodine, technetium can be used as an alternative.
How is the thyroid scan performed?
A thyroid scan is an outpatient procedure usually done in the nuclear medicine section of a hospital. This is usually part of the radiology department.
If you have a thyroid scan, you will be asked to take a drink, or swallow a pill containing the iodine. You will then wait for the iodine to be taken up by the thyroid - usually about 4 hours. At this time you lie under a scintography camera, and it will take pictures which correlate directly to the amount of iodine taken up by the thyroid. This is done by counting the intensity and location of the gamma rays emitted by the radioactively labeled iodine. You then leave the hospital, and return in 24 hours to have a second scan performed in the same manner.
There are no limitations during this 24 hour interval except that you will be asked to take precautions when you urinate. This is because the radioactive iodine is removed from your body by the urine, and it is safer to have others avoid contact with your urine during this time. Be sure to let the doctor performing the test know if you have an iodine allergy, or if you have ingested a lot of iodine-containing foods (like sushi) prior to the test.
Quick GuideHyperthyroidism Symptoms and Treatment
When is thyroid scanning helpful?
A thyroid scan can provide information on the size and shape of the gland as well as the overall activity of the gland (is the whole thyroid gland overactive or underactive?).
For example, thyroid scanning is used to determine how active thyroid tissue is in manufacturing thyroid hormone. This feature can determine whether inflammation of the thyroid gland (thyroiditis) is present. It can also detect the presence and degree of overactivity of the gland (hyperthyroidism ). In this case the scan reveals increased iodine uptake by the whole gland.
In addition, a thyroid scan can provide information on specific areas within the thyroid gland and can help to determine whether any localized areas are hyperfunctioning or under functioning compared to the rest of the gland. In these cases spots appear on the image corresponding to areas that take up iodine differently from the rest of the gland.
Thyroid scanning is especially helpful in evaluating thyroid nodules, particularly after a fine needle aspiration biopsy has failed to provide a diagnosis. A scan will reveal whether a thyroid nodule is "functioning" or "nonfunctioning". Doctors refer to hyper functioning nodules of the thyroid (those that are actively taking up iodine to produce thyroid hormone more so than surrounding thyroid tissue) as "hot" nodules, and these hyperfunctioning areas are seen on the image of the thyroid gland. A nonfunctioning nodule does not take up iodine and produces a localized "cold" area on the image of the thyroid gland.
In addition, thyroid scanning can be done to help determine if thyroid cancer has spread beyond the bed of the thyroid in the neck. For this purpose, usually a whole body thyroid scan is performed.
What is significant about whether a nodule is "hot" or "cold?"
Functioning or "hot" nodules only rarely are from cancer. Nearly all thyroid cancers are nonfunctioning or "cold" nodules. However, even among "cold" nodules, cancer is infrequent (less than 5 percent of cases).
Thyroid Scan Safety and Efficacy
While the thought of taking something "radioactive" is not very appealing, it is important to remember that iodine concentrates only in thyroid tissue, making this test safe and also quite specific for thyroid disorders.
A thyroid scan can provide information on both the structure as well as the function of the thyroid gland. This information can help you and your physician determine if further investigations, procedures, or medications are medically necessary.
Medically reviewed by John A. Seibel, MD; Board Certified Internal Medicine with a subspecialty in Endocrinology & Metabolism
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Fine-Needle Aspiration Biopsy of the ThyroidFine needle aspiration biopsy of the thyroid is used to obtain tissue for analysis. Fine needle aspiration is also performed to treat thyroid cysts. The fine needle aspiration biopsy procedure may be recommended to make the diagnosis and/or select therapy of a thyroid nodule. Fine needle aspiration biopsy may also be recommended to drain or shrink a thyroid cyst.
Graves' DiseaseGraves' disease is an autoimmune disease that affects the thyroid. Some of the symptoms of Graves' disease include hand tremors, rapid heartbeat, trouble sleeping, enlarged thyroid, thinning of the skin or fine brittle hair. Causes of Graves' disease are thought to be multifactorial such as genes, gender, stress, and infection. Treatment for Graves' disease is generally medication.
Hashimoto's ThyroiditisHashimoto's thyroiditis is the most common cause of hypothyroidism in the US. This conditions is caused by inflammation of the thyroid gland. Symptoms may include:
- weight gain,
- cold intolerance,
- excessive sleepiness,
- dry or coarse hair,
- difficulty swallowing,
- a lump in the front of the throat, and
- many more.
Hyperthyroidism is an excess of thyroid hormone resulting from an overactive thyroid gland. Symptoms can include
- increased heart rate,
- weight loss,
- frequent bowel movements,
- depression, and
- cognitive slowing.
Treatment is by medication, the use of radioactive iodine, thyroid surgery, or reducing the dose of thyroid hormone.
Hyperthyroidism SlidesWhat is hyperthyroidism? Hyperthyroidism occurs when an overactive thyroid gland produces an excessive amount of thyroid hormones. Learn hyperthyroidism causes, symptoms, and treatment.
Hypothyroidism is any state in which thyroid hormone production is below normal. Normally, the rate of thyroid hormone production is controlled by the brain by the pituitary gland. Hypothyroidism is a very common condition and the symptoms of hypothyroidism are often subtle, but may include
- memory loss,
- hair loss, and
There are a variety of causes of hypothyroidism, and treatment depends on the cause.
Thyroid Blood TestsThyroid blood tests determine the adequacy of the levels of thyroid hormones in in a patient. The blood tests can determine if the thyroid gland's hormone production is normal, overactive , or underactive. The level of thyroid hormones may help to diagnose hypothyroidism or hyperthyroidism. The test may also point to other diseases of conditions of the thyroid gland.
Thyroid CancerThere are four major types of thyroid cancer: papillary, follicular, medullary, and anaplastic thyroid cancer. Tumors on the thyroid are referred to as thyroid nodules. Symptoms of thyroid cancer include swollen lymph nodes, pain in the throat, difficulty swallowing, hoarseness, and a lump near the Adam's apple. Treatment usually involves chemotherapy, surgery, radioactive iodine, hormone treatment or external radiation and depends upon the type of thyroid cancer, the patient's age, the tumor size, and whether the cancer has metastasized.
Thyroid DisordersThere are several types of thyroid disorders including hypothyroidism, hyperthyroidism, goiters, thyroid nodules, and thyroid cancer. Symptoms vary by condition. Diagnosis is made with blood tests, scans, ultrasound, or biopsy. Treatments depend on the disorder and can include medication or surgery.
Thyroid NodulesThyroid nodules are the most common endocrine problem in the United States. The term "thyroid nodule" refers to any abnormal growth that forms a lump in the thyroid gland. The vast majority of thyroid nodules are benign.
Thyroid Peroxidase TestThe thyroid peroxidase test measures the level of an antibody that is directed against thyroid peroxidase (TPO). A presence of TPOAb in the blood reflects a prior attack by the body's immune system on thyroid tissue. A positive thyroid peroxidase test may signal chronic thyroiditis. Other autoimmune disorders, however, may have a positive TPOAb test.
Illustrations of ThyroidThe thyroid is a butterfly-shaped gland located in the front of the neck just below the Adams apple. See a picture of the Thyroid and learn more about the health topic.
Thyroid SlideshowLearn about thyroid problems such as hyperthyroidism, hypothyroidism, thyroid cancer, and more. Discover symptoms and treatments for various thyroid problems.
ThyroiditisThyroiditis is the inflammation of the thyroid gland. The inflamed thyroid gland can release an excess of thyroid hormones into the blood stream, resulting in a temporary hyperthyroid state. Some forms of thyroiditis can be diagnosed based on tenderness and enlargement of the thyroid gland. A thyroid scan sometimes is used in making the diagnosis. Thyroiditis can also be diagnosed with a biopsy of the thyroid gland.