Correlation between the thyroid computed tomography value and thyroid function in hyperthyroidism: a retrospective study

Objective Radioiodine (I-131) therapy for hyperthyroidism is a well-established and safe treatment option. This study aimed to investigate the relationship between the computed tomography (CT) value and the function and volume of the thyroid gland by identifying the factors that induce changes in the CT value of patients with hyperthyroidism. Methods This retrospective study evaluated 38 patients with Graves' disease and 10 patients with Plummer disease. To obtain the mean CT value and volume of the thyroid gland, the entire thyroid gland was set as the region of interest. A test dose of 3.7 MBq I-131 was administered before initiating I-131 therapy, and the radioiodine uptake (RIU) rate was assessed after 3, 24, 96, and 168 h. An approximate curve was plotted based on the RIU values obtained, and the effective half-life (EHL) was calculated. The correlation between the mean CT value and the volume of the thyroid gland, 24-h RIU, EHL, and the free triiodothyronine (FT3), free thyroxine (FT4), thyroid-stimulating hormone (TSH), and TSH receptor antibody (TRAb) levels was evaluated. Results The CT value exhibited a significant positive correlation with EHL in patients with Graves' disease (r = 0.62, p < 0.0001) as well as patients with Plummer disease (r = 0.74, p < 0.05). However, it did not display any correlation with the remaining parameters. Conclusion The CT value is significantly correlated with EHL, suggesting that it reflects thyroid function and is mainly related to the factors associated with iodine discharge.