Radioactive iodine uptake on thyroid scanning is typically high in Graves disease and low in other conditions. Which statement is correct?

Radioactive iodine uptake on thyroid scanning is typically high in Graves disease and low in other conditions. Which statement is correct?

• A. Low uptake in Graves, high in other conditions
• B. High uptake in Graves, low in other conditions
• C. No uptake in Graves
• D. Uniform uptake across all thyroid conditions

Answer: (B)

Radioactive iodine uptake helps distinguish causes of thyrotoxicosis by showing how actively the thyroid is synthesizing hormone. In Graves disease, the entire gland is diffusely overactive from autoimmune stimulation of the TSH receptor, so it traps and incorporates iodine at a high rate, producing high uptake on scan. In most other conditions that cause thyrotoxicosis, either the hormone is released from damaged tissue (as in thyroiditis), or the overactivity is patchy or nodular, so the overall uptake tends to be low or only focal. The statement reflects this general pattern: Graves disease shows high uptake, whereas many other thyroid disorders associated with thyrotoxicosis show low uptake. There are exceptions—for example, toxic nodular disease can show focal or higher uptake in the nodules—but the classic teaching for the scan pattern is that Graves is high uptake and other non-Graves conditions are typically low uptake.

Radioactive iodine uptake helps distinguish causes of thyrotoxicosis by showing how actively the thyroid is synthesizing hormone. In Graves disease, the entire gland is diffusely overactive from autoimmune stimulation of the TSH receptor, so it traps and incorporates iodine at a high rate, producing high uptake on scan. In most other conditions that cause thyrotoxicosis, either the hormone is released from damaged tissue (as in thyroiditis), or the overactivity is patchy or nodular, so the overall uptake tends to be low or only focal.

The statement reflects this general pattern: Graves disease shows high uptake, whereas many other thyroid disorders associated with thyrotoxicosis show low uptake. There are exceptions—for example, toxic nodular disease can show focal or higher uptake in the nodules—but the classic teaching for the scan pattern is that Graves is high uptake and other non-Graves conditions are typically low uptake.