What are some possible causes of a thyroid scan in which there is no uptake or minimal uptake of radiotracer by the thyroid gland?
When there is no thyroid radiotracer uptake observed on a thyroid scan, there are several potential causes. Patients may have thyroiditis, in which the inflammatory process has destroyed most or all functioning thyroid tissue. Such patients can be hyperthyroid or hypothyroid depending on the time course of the disease. Other causes of minimal radiotracer uptake in the thyroid gland include exogenous sources of thyroid hormone (some patients take thyroid hormone as a form of diet pill) or iodine (e.g., recent iodinated contrast agent administration, ingestion of drugs containing iodine such as amiodarone, consumption of high-salt or seafood diets, and ingestion of alternative medicine supplements). Exogenous sources of thyroid tissue, such as struma ovarii (thyroid tissue in a monodermal ovarian teratoma), should also be considered in such patients.