This procedure is used to see if the thyroid gland is working properly. The thyroid gland is located in the neck just below the Adam's apple and makes hormones that are important in metabolism.
A thyroid scan is usually done when a lump is felt in the thyroid gland or when there is an abnormal increase or decrease of thyroid hormone levels in the blood.
The person is asked to either drink a liquid or take a pill that contains radioactive iodine. The radioactive iodine goes into the thyroid gland over the next several hours. About four hours after taking the iodine, the person is asked to lie down on a table below a special camera that can detect the radioactive material.
While the person lies very still, the camera takes pictures of the thyroid gland. It takes about 30 to 60 minutes to take all the required pictures. Usually, the person is asked to come back 24 hours later to have a second set of pictures taken, which only takes about 5 minutes.
The pattern of the pictures can tell the healthcare professional what may be wrong with the thyroid gland. Some areas of the gland may take up more radioactive iodine than others. The pattern of uptake often suggests a specific disease, which can guide the treatment.
For example, the thyroid scan may reveal an area that is suspicious for thyroid cancer. In this case, surgery may be needed to remove it. Or the scan may show that the thyroid gland is overactive and will respond to medications. The healthcare professional will discuss the results and treatment options.
Harrison's Principles of Internal Medicine, 1998, Fauci et al.