In Hashimoto's thyroiditis, how is radioiodine uptake typically?

• A. High uptake.
• B. Low uptake and often transient.
• C. Normal uptake.
• D. Absent uptake.

Answer: (B)

Hashimoto's causes autoimmune destruction of thyroid follicular cells, so the gland’s ability to trap and incorporate iodine drops. That reduced functional tissue leads to decreased radioactive iodine uptake on a scan. The “often transient” part reflects the inflammatory phase where hormone may be released from damaged cells while new hormone synthesis is impaired, keeping uptake low during that period. Over time, as destruction persists and hypothyroidism ensues, uptake generally remains low. This pattern helps distinguish Hashimoto's from conditions like Graves disease, where uptake is typically high due to increased synthesis.