Assessment of thyroid iodine accumulation following repeated iodinated contrast media administration using dual-energy computed tomography in a rabbit model.

Repeated exposure to iodinated contrast media (ICM) may induce thyroid dysfunction but supporting radiological and histological evidence remains limited. This study aimed to evaluate whether repeated ICM administration induces iodine accumulation and related functional and histological changes in the thyroid. This prospective 8-week study involved 30 male New Zealand white rabbits (0.8–1.2 kg, < 1 year) assigned to four groups. The control group (n = 8) received 0.9% sodium chloride solution, while experimental groups received intravenous iohexol three times weekly at 1.6 mL/kg (n = 7), 6.0 mL/kg (n = 7), or 12.0 mL/kg (n = 8). Non-contrast thyroid dual-energy computed tomography (DECT) was performed weekly to quantify iodine accumulation, expressed as the thyroid enhancement ratio (TER) relative to paraspinal muscle. Serum free thyroxine (fT4), free triiodothyronine (fT3), thyroid-stimulating hormone, and creatinine were measured at baseline, week 4, and week 8. Histological analysis was performed at week 8. At week 8, TER was significantly higher in the 6.0 mL/kg (2.59 ± 0.89) and 12.0 mL/kg (2.79 ± 0.77) groups than in controls (1.15 ± 0.42) and the 1.6 mL/kg group (1.32 ± 0.46) (all P < 0.05). While transient fT4 and fT3 elevations occurred and nodular hyperplasia, follicular atrophy, and inflammation were more frequent in high-dose groups, neither showed statistically significant intergroup differences (both P > 0.05). In conclusion, repeated intravenous administration of high-dose ICM in rabbits was associated with increased iodine accumulation in the thyroid gland, as quantified by DECT. However, a transient rise in serum thyroid hormone levels, as well as more frequent histopathological changes, did not reach statistical significance.