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A thyroid scan is a procedure used to evaluate the health of your thyroid gland. The scan takes advantage of the thyroids ability to collect radioactive substances. During a scan, a special camera takes pictures of your thyroid after you have been given a radioactive substance.
The thyroid gland is located in the front of the neck, below the Adams apple. It is made up of two roundish lobes, which are connected by a middle part. It is about two inches across and is shaped like a butterfly. The thyroid controls many body functions including heartbeat, blood pressure, and body temperature. It is also responsible for childhood growth and metabolism. Metabolism refers to how your body turns food into energy.
A thyroid scan is usually ordered when laboratory tests or a neck examination suggest that the thyroid is enlarged. A scan can:
- Test how well the thyroid is working
- Diagnose abnormalities
- Determine if there are lumps, called nodules, on the thyroid
- Help determine the cause of an overactive thyroid
- Check if known thyroid cancer has spread
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Risk Factors for Complications During the Procedure Thyroid scans are associated with very few risks. Tell your doctor if you: Have an allergy to any medicationsAre (or might be) pregnant or breastfeeding, because the test could expose the baby to radiationTake any medications on a regular basis, as some can interfere with test results If you recently had any x-rays or other thyroid tests What to Expect Prior to ProcedureFor a period of time before the scan, you may be asked to avoid certain food or medications that can interfere with the results (like thyroid medications and shellfish).Jewelry, dentures, and other metallic objects will be removed.You may be asked not to eat or drink anything after midnight on the day before the test.Your doctor may order some tests to measure the amount of thyroid hormone in your blood. AnesthesiaNo anesthesia is necessary. Description of the ProcedureThe procedure is performed by a trained technician in the radiology department of a hospital. You will be given a radioactive substance, which is either injected into a vein or given in the form of a liquid or a pill. Once the substance has had time to collect in the thyroid, the scan begins. You will lie on your back with your head tilted back. You will be asked to lie very still at certain times. The technician will use a scanner to take pictures of your thyroid from different angles. The camera is not an x-ray and does not expose you to more radiation.
After ProcedureThere is no recovery period after the scan. You may go back to work or resume other normal activities. How Long Will It Take?If the radioactive substance is injected, the scan can be performed 30 to 60 minutes later. If you take the substance in liquid form or as a pill, you will wait 4 to 6 hours before having the scan. The scan itself takes about half an hour. Will It Hurt?There is no pain associated with a thyroid scan. There may be times when you find it uncomfortable to lie still with your head tilted backward. Possible ComplicationsThere is a very low risk of complications with this procedure. The radioactivity you are exposed to is similar to a normal x-ray. It generally does not cause side effects or negative reactions. Average Hospital StayA thyroid scan is an outpatient procedure. Postoperative CareThe majority of the radioactive substance will leave your body within a day or two. You are not at risk for exposing other people to radiation, so you can interact normally with them. Outcomes The pictures of the scan take about an hour to develop, and then a radiologist will examine them. A scan tells the doctor if the thyroid: Has a normal function and appearance; if so, then there is no indication of cancerShows abnormal size, shape, or positionIs absorbing the expected amount of radioactive substance. The radioactive substance that is absorbed by the thyroid shows up on the scan as lighter or darker patches. If the thyroid is not functioning normally, the results of the scan are considered: Coldwhen thyroid absorbs less radioactive substance than is expectedHotwhen thyroid absorbs more radioactive substance than is expected TreatmentWhen a cold nodule is found, the follow-up treatment is a biopsy of the nodule. If the nodule has already had a biopsy, then you should have the nodule removed by an experienced thyroid surgeon. Thyroid cancer is usually curable.
If the nodule is hot, a biopsy is not necessary since cancer is rare in a hot nodule. However, any nodule that is not removed should be examined every 6 to 12 months to check for changes in size or function. Call Your Doctor If Any of the Following OccursCall your doctor if you experience any unusual pain or discomfort. RESOURCES: American Thyroid Association, Inc.http://www.thyroid.org Thyroid Foundation of America, Inc.http://www.allthyroid.org CANADIAN RESOURCES: Canadian Health Networkhttp://www.canadian-health-network.ca/ The Thyroid Foundation of Canadahttp://www.thyroid.ca References: Beers, MH, Fletcher AJ, Jones TV, et al. The Merck Manual of Medical Information: Second Home Edition. Whitehouse Station, NJ: Merck Research Laboratories; 2003. Diagnostic tests: thyroid scan. Harvard Medical School Family Health Guide website. Available at: www.health.harvard.edu/fhg/diagnostics . Accessed August 2005. Thyroid-Cancer.net: what is a thyroid scan? Johns Hopkins Thyroid Tumor Center website. Available at: www.thyroid-cancer.net/topics/what+is+a+thyroid+scan . Accessed August 24, 2005. Thyroid nodule. Dynamed website. Available at: http://dynamedical.com/dynamed.nsf?opendatabase . Accessed August 24, 2005.
Thyroid nodules: symptoms, causes, diagnosis, treatment. American Thyroid Foundation website. Available at: http://thyroid.org . Accessed August 24, 2005. Thyroid nuclear medicine scan. Dr. Joseph F Smith Medical Library website. Available at: www.chclibrary.org/micromed/00068040.html . Accessed August 24, 2005. Thyroid scan. Medline Plus (National Library of Medicine and the National Institutes of Health) website. Available at: http://www.nlm.nih.gov/medlineplus/ency/article/003829.htm . Accessed August 24, 2005. Last reviewed November 2007 by Rosalyn Carson-DeWitt, MDPlease be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.