Abstract:
Objective To study the effect of urinary iodine level on the technicium (99Tcm)-pertechnetate uptake function of the thyroid of patients with Graves' hyperthyroidism.
Methods One-hundred newly diagnosed patients with Graves' hyperthyroidism, including 20 males and 80 females (40.33±11.85 years old), from the First Affiliated Hospital of China Medical University from July to November 2018 were selected. Urinary iodine and creatinine concentrations were measured in urine samples from all patients, and patients were divided into low, medium, and high urinary iodine groups according to the standard of urinary iodine levels (≤100, 101−249, and ≥250 μg/gCr, respectively) and divided into seafood and no seafood intake groups according to whether the patients had eaten seafood 2 weeks before the examination. All patients underwent single-photon emission computed tomography (SPECT)/computed tomography (CT) imaging to compute their thyroid-to-cervical soft tissue (T/C) ratio. Single-factor one-way analysis of variance was used for the comparison among groups, and least significant difference (LSD)-t test was used for the pairwise comparison among groups. Mann-Whitney U and t tests were used for comparison between two groups. Pearson test was used for correlation analysis.
Results (1) The T/C ratios of patients with low, medium, and high urinary iodine levels were 24.18±8.43, 20.35±6.94, and 16.81±4.93, respectively, and the difference was statistically significant (F=5.40, P=0.006). The T/C ratios of the low and middle urinary iodine level groups were higher than that of the high urinary iodine level group with statistically significant differences (t=3.05, 2.38; P=0.003, 0.019), whereas the T/C ratios of the low and middle urinary iodine level groups were not statistically different. Urinary iodine level was negatively correlated with T/C ratio, and the difference was statistically significant (r=−0.24, P=0.023). (2) The levels of urinary iodine (M(P25, P75)) in the seafood and non-seafood groups were 229.2(163.06, 400.16) and 178.97(118.86, 245.54) μg/gCr, respectively, with statistically significant difference (Z=2.87, P=0.004). The T/C ratios of the two groups were 16.65±6.41 and 21.03±6.73, respectively, with statistically significant differences (t=3.10, P=0.003).
Conclusion Elevated urinary iodine level in patients with Graves' hyperthyroidism remarkably inhibits the thyroid's 99Tcm-pertechnetate uptake function, and eating seafood before imaging increases the urinary iodine level in patients with Graves' hyperthyroidism.