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.
What can I expect with a thyroid scan?
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 that 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.
What does a thyroid scan do?
- 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 hyperfunctioning 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.
- CDC Warns of Potentially Fatal Bacterial Illness on U.S. Gulf Coast
- Helping Others as Volunteers Helps Kids 'Flourish': Study
- FDA Approves Pfizer's RSV Shot for Older Adults
- What to Do When Tough-to-Treat Lymphoma Strikes During Pregnancy
- Rate of Pregnant U.S. Women Who Have Diabetes Keeps Rising
- More Health News »
What do the results of a thyroid scan mean?
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).
How safe is a thyroid scan?
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.
Health Solutions From Our Sponsors
National Institutes of Health
Top Thyroid Scan Related Articles
CancerCancer is a disease caused by an abnormal growth of cells, also called malignancy. It is a group of 100 different diseases, and is not contagious. Cancer can be treated through chemotherapy, a treatment of drugs that destroy cancer cells.
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.
Hyperthyroidism is an excess of thyroid hormone due to an overactive thyroid gland. Symptoms can include increased heart rate, weight loss, heart palpitations, frequent bowel movements, depression, fatigue, fine or brittle hair, sleep problems, thinning skin, and irregular vaginal bleeding.
Graves' disease is the most common cause of hyperthyroidism. Many other health problems or taking excess thyroid hormone medication can cause an overactive thyroid gland. Treatment for the condition is with medication, radioactive iodine, thyroid surgery (rarely), or reducing the dose of thyroid hormone. No diet has been shown to treat hyperthyroidism or its symptoms and signs.
Hyperthyroidism: Symptoms, Treatment, MedicationWhat are the symptoms of hyperthyroidism? What causes hyperthyroidism? What happens when you take thyroid medication? Hyperthyroidism occurs when an overactive thyroid gland produces an excessive amount of thyroid hormone. Learn hyperthyroidism causes, symptoms, and treatment.
HypothyroidismHypothyroidism 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 constipation, memory loss, hair loss, and depression. There are a variety of causes of hypothyroidism, and treatment depends on the cause.
Parathyroidectomy SurgeryParathyroidectomy is the removal of one or more of the parathyroid glands to treat hyperparathyroidism. Risks of parathyroidectomy include:
- paralysis of the vocal cords,
- difficulty swallowing thin liquids,
- difficulty breathing,
- and drug reactions.
- damage to the recurrent laryngeal nerve,
- bleeding or hematoma,
- problems maintaining calcium levels in the blood,
- need for further and more aggressive surgery,
- need for a limited or total thyroidectomy,
- prolonged pain,
- impaired healing,
- and recurrence of the tumor.
Symptoms of 12 Serious Diseases and Health ProblemsLearn how to recognize early warning signs and symptoms of serious diseases and health problems, for example, chronic cough, headache, chest pain, nausea, stool color or consistency changes, heartburn, skin moles, anxiety, nightmares, suicidal thoughts, hallucinations, delusions, lightheadedness, night sweats, eye problems, confusion, depression, severe pelvic or abdominal pain, unusual vaginal discharge, and nipple changes.
The symptoms and signs of serious health problems can be caused by strokes, heart attacks, cancers, reproductive problems in females (for example, cancers, fibroids, endometriosis, ovarian cysts, and sexually transmitted diseases or STDs), breast problems (for example, breast cancer and non-cancer related diseases), lung diseases (for example, chronic obstructive pulmonary disease or COPD, lung cancer, emphysema, and asthma), stomach or digestive diseases (for example, cancers, gallbladder, liver, and pancreatic diseases, ulcerative colitis, or Crohn's disease), bladder problems (for example, urinary incontinence, and kidney infections), skin cancer, muscle and joint problems, emotional problems or mental illness (for example, postpartum depression, major depression, post-traumatic stress disorder (PTSD), mania, and schizophrenia), and headache disorders (for example, migraines, or "the worst headache of your life), and eating disorders and weight problems (for example, anorexia or bulimia).
Thyroid Blood Tests
Thyroid 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 Disorders Symptoms and SignsThyroid diseases and disorders are caused because the body either makes too much or too little thyroid hormones, which are necessary for vital functions of the body.
Thyroid disease and disorder symptoms and signs depend on the type of the thyroid problem. Examples include heat or cold intolerance, sweating, weight loss or gain, palpitations, fatigue, dry skin, constipation, brittle hair, joint aches and pains, heart palpitations, edema, feeling bloated, puffiness in the face, reduced menstrual flow, changes in the frequency of bowel movements and habits, high cholesterol, hoarseness, brittle hair, difficulty swallowing, shortness of breath, a visible lump or swelling in the neck, tremors, memory problems, depression, nervousness, agitation, irritability, or poor concentration.
Thyroid problems are more common in women.
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 Peroxidase TestThe thyroid peroxidase test measures the level of an antibody that is directed against thyroid peroxidase (TPO). The 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.
Your Thyroid: Common Thyroid Problems and Diseases ExplainedLearn about thyroid problems such as hyperthyroidism, hypothyroidism, thyroid cancer, and more. Discover symptoms and treatments for various thyroid problems.
Thyroid QuizYour unexplained change in weight could indicate a thyroid condition. Take the Thyroid Quiz to learn about common symptoms and treatments of overactive and underactive thyroid disorders.
Cancer: Visual Guide to Thyroid CancerFind out the symptoms of thyroid cancer, and learn how to treat it after you get a diagnosis.