Patterns of thyroid radioiodine uptake: Jordanian experience

This study aimed to determine the reference range of 24-h radioiodine uptake in euthyroid Jordanians, as well as the reference ranges for patients with diffuse and nodular hyperthyroidism. In addition, radioiodine uptake ranges were determined for those patients with Hashimoto's thyroiditis and early-phase subacute thyroiditis.

The medical records of 285 Jordanian patients referred for (131)I thyroid scintiscans and 24-h radioiodine uptake tests were reviewed. The patients were referred because of a presumed-certain thyroid disorder. The patients included those who were euthyroid or who had Graves' disease, toxic nodules, Hashimoto's thyroiditis, or subacute thyroiditis. Mean radioiodine uptake and the 95% confidence interval were determined in each group. A comparison was made between groups.

Mean uptake (+/-SD) for the euthyroid group, toxic-nodule group, and Hashimoto's thyroiditis group was 15% +/- 7%, 19% +/- 9%, and 19% +/- 15%, respectively, and these values were not significantly different from each other (P > 0.05). Mean uptake for the subacute thyroiditis group and Graves' disease group was 3% +/- 4% and 40% +/- 14%, respectively, and both values were significantly different from other groups (P < 0.05).

The reference range of radioiodine uptake in Jordan is comparable to that reported in North America and Europe because Jordanians likely have a sufficient daily intake of stable iodine. Radioiodine uptake discriminates between euthyroid patients, subacute thyroiditis patients, and Graves' disease patients. Radioiodine uptake in toxic-nodule patients is diagnostic only if combined with image findings. Mean radioiodine uptake in Hashimoto's thyroiditis is higher than the euthyroid mean but has a wide range.