When taking thyroid scans, cold and hot nodules are terms to describe findings of the thyroid that are very active or less active in uptake, according to Wellsphere. A small amount of radioactive iodine is given to the patient to indicate how much iodine is taken up by the thyroid.
Nodules showing increased uptake from the rest of the thyroid are called hot nodules even when indicating a difference in just one nodule in the thyroid, states Wellsphere. Cold nodules are other nodules in the thyroid taking up less iodine. Hot nodules make the bulk of thyroid hormone, while cold nodules do not. When radioactive iodine scanning determines the thyroid nodule to be hot, chances are great the nodule is benign as hot nodules are almost never malignant.
Approximately 10 percent of cold nodules discovered through iodine scanning are found to be malignant, notes Wellsphere. While radioactive iodine scanning is a good indicator of potential problems with thyroid nodules, it is not a definitive diagnosis. A tissue sample or needle biopsy is the recommended method to determine if a thyroid nodule is cancerous. Both location and intensity of iodine uptake in the thyroid aid in determining problems with thyroid nodules.