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What is a cold nodule?

Diana Meeks
Diana Meeks on behalf of Sigma Nursing
Family Practitioner
A cold nodule is identified when radioactive material is used to examine the thyroid with a scanner. Nodules that collect less radioactive material than the surrounding thyroid tissue are considered “cold.” A nodule that is cold does not make thyroid hormone. Cold nodules may be benign (not cancer) or malignant (cancer). Cold nodules are sometimes called hypofunctioning nodules.

This answer is based on source information from the National Cancer Institute.
Dr. Jack Merendino, MD
Endocrinology Diabetes & Metabolism
The term “cold” nodule means that a thyroid nodule is not as metabolically active in making thyroid hormone as normal thyroid tissue, and should be contrasted with “warm” thyroid nodules that are about as active as normal thyroid tissue or “hot” nodules which are more active. The term has nothing to do with temperature. It results from doing a nuclear medicine thyroid scan with radioactive iodine. Iodine is absorbed from the bloodstream by thyroid cells as they are making thyroid hormone and if a lot of iodine is accumulated within a nodule it is deemed “hot” whereas one that takes up very little is “cold.” 

Many people, including many doctors, are confused about what it means to have a cold nodule. Most thyroid cancers occur in cold nodules, but more than 90% of nodules are cold, so it’s no surprise that they also contain the most cancers. Diagnosing a thyroid nodule to be benign or cancerous is much better done using ultrasound and fine needle aspiration biopsy. Thyroid scanning to determine whether a nodule is cold provides very little useful information in most cases.  

A thyroid scan is an important test in a person who is hyperthyroid -- i.e., someone who has an overactive thyroid. The test will distinguish among the causes of hyperthyroidism, including those cases that result from one or more “hot” nodules. This can be very important in deciding how to treat the hyperthyroidism. 

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.