MedTerms Medical Dictionary

Thyroid scan: An image taken of the thyroid gland after radioactive iodine is taken by mouth. The thyroid gland is in front of the neck:

Thyroid scanning is a nuclear medicine procedure. As the thyroid gland accumulates radioactive material (usually, radioactive technetium or iodine), the gland produces an image.

Thyroid scanning is used to determine how active the thyroid is in manufacturing thyroid hormone. This 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) or, conversely, it can determine the presence and degree of underactivity of the gland (hypothyroidism).

Thyroid scanning is helpful in evaluating thyroid nodules, particularly after a fine needle aspiration biopsy of a nodule has failed to provide a definitive diagnosis. A scan will reveal whether a thyroid nodule is functioning or nonfunctioning. A functioning nodule actively takes up iodine to produce thyroid hormone and produces a localized "hot" area on the image of the thyroid gland. A nonfunctioning nodule does not take up iodine and so produces a "cold" area on the image of the thyroid gland. Functioning or "hot" nodules only rarely are from cancer. Nearly all thyroid cancers are nonfunctioning or "cold" nodules. Moreover, even among "cold" nodules, cancer is infrequent (less than 5 percent of cases).

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Find a medical definition by using the A-Z listing (select a letter)

Copyright © 1996-2003 MedicineNet, Inc. All rights reserved.
MedicineNet, Inc. does not endorse any of the services or products offered on this page.

Information in the MedTerms Medical Dictionary is provided for informational purposes only and is not a substitute for professional medical advice. You should not use this information for diagnosing or treating a medical or health condition. You should carefully read all product packaging. If you have or suspect you have a medical problem, promptly contact your professional healthcare provider.

Use the A-Z listing (select a letter) to find a definition

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z