Which thyroid condition is associated with high radioactive iodine uptake on a thyroid scan?

Which thyroid condition is associated with high radioactive iodine uptake on a thyroid scan?

• A. Graves disease
• B. Hashimoto thyroiditis
• C. Subacute thyroiditis
• D. Toxic multinodular goiter

Answer: (A)

High uptake on a radioactive iodine scan signals that the thyroid is actively synthesizing hormone rather than merely leaking it from damaged tissue. Graves disease fits this pattern because autoantibodies stimulate TSH receptors across the whole gland, causing diffuse, uniform overactivity and increased iodine trapping. In this scenario, the scan shows high, global uptake rather than focal or low uptake. In contrast, Hashimoto thyroiditis involves autoimmune destruction of thyroid tissue, typically leading to hypothyroidism and low iodine uptake. Subacute thyroiditis is an inflammatory, destructive process that releases preformed hormone, often with low uptake because the damaged tissue cannot trap iodine effectively. Toxic multinodular goiter causes hyperthyroidism from one or more autonomous nodules; the scan usually shows patchy or focal uptake corresponding to those nodules rather than diffuse high uptake across the entire gland.

High uptake on a radioactive iodine scan signals that the thyroid is actively synthesizing hormone rather than merely leaking it from damaged tissue. Graves disease fits this pattern because autoantibodies stimulate TSH receptors across the whole gland, causing diffuse, uniform overactivity and increased iodine trapping. In this scenario, the scan shows high, global uptake rather than focal or low uptake.

In contrast, Hashimoto thyroiditis involves autoimmune destruction of thyroid tissue, typically leading to hypothyroidism and low iodine uptake. Subacute thyroiditis is an inflammatory, destructive process that releases preformed hormone, often with low uptake because the damaged tissue cannot trap iodine effectively. Toxic multinodular goiter causes hyperthyroidism from one or more autonomous nodules; the scan usually shows patchy or focal uptake corresponding to those nodules rather than diffuse high uptake across the entire gland.