Why can be used to treat thyroid cancer if it appears as a cold nodule on thyroid scintigraphy?
Although a cold nodule on thyroid scintigraphy does not appear to take up any of the radioactive iodine, its inactive appearance is in comparison to the background activity of the normal gland. Thyroid cancer cells generally take up the iodine but not as well as normal tissues. For this reason, thyroid cancer appears cold on the scan but can still take up enough iodine for therapy to be effective. To enhance the therapeutic effects of 131 I therapy, the normal thyroid is surgically removed. By eliminating much of the normal thyroid tissue, there is a better chance for any remaining thyroid cancer cells to take up 131 I. The hope is that by removing the thyroid gland and keeping the patient off of thyroid replacement hormones, the TSH level will be greater than 30 IU/L, which should maximally stimulate any thyroid cancer cells left over in the body to take up 131 I. Patients are also usually prescribed a low-iodine diet to “starve” any thyroid cells, further maximizing uptake of 131 I .