The effect of radioiodine treatment on the characteristics of TRAb in Graves' disease

Abstract

Background: Graves' disease (GD) is one of the most common autoimmune thyroid diseases (AITDs) in humans, and thyrotropin receptor antibody (TRAb) is a characterized autoantibody in GD. The use of radioactive iodine therapy (RAI) for GD treatment is increasing.

Objectives: We studied the biological properties of TRAb and evaluated the effect of RAI therapy on TRAb in GD patients.

Methods: In total, 225 patients (22 onset GD patients without ¹³¹I therapy, 203 GD patients treated with ¹³¹I therapy) and 20 healthy individuals as normal controls were included in this study. Clinical assessments were performed, and we examined in vitro the biological properties of TRAb in the 22 onset GD patients and 20 controls as well as 84 GD patients with ¹³¹I therapy.

Results: Serum TRAb and thyroid peroxidase antibody (TPOAb) levels increased in the initial year of RAI treatment, and both antibodies decreased gradually after one year. After 5 years from radioiodine treatment, TRAb and TPOAb levels decreased in 88% and 65% of GD patients, respectively. The proportion of patients positive for thyroid-stimulatory antibody (TSAb) was significantly higher in the 7-12-month group, and thyroid-blocking antibody (TBAb) levels were elevated after one year in half of the patients who received ¹³¹I treatment.

Conclusions: Treatment of GD patients with radioiodine increased TPOAb and TRAb (their main biological properties were TSAbs) within the first year after therapy, and the main biological properties of elevated TRAb were TBAbs after 1 year.

Fig. 1

Time course changes in antibodies after ¹³¹I therapy. A and B Show time course changes in TRAb and TPOAb in Graves’ disease patients before and after ¹³¹I therapy. *denotes p < 0.05, ***denotes p < 0.001, ^###p < 0.001 represents the 1–6 months group versus 13–60 months group and >60 months group, ^&&&p < 0.001 represents the 7–12 months group versus 13–60 months group and >60 months group, ^$$p < 0.01 represents the 13–60 months group versus >60 months group

Fig. 2

Changes in TRAb and TPOAb at different times after ¹³¹I treatment. This picture shows the time course discrepancy of the GD patient ratio with different TRAb changes (A) and TPOAb changes (B) after RAI therapy. The p value was obtained by the Trend Test

Fig. 3

Bioactivity of TRAb in GD patients treated with ¹³¹I therapy. TRAb bioactivity was measured in 22 onset Graves’ disease patients without radioiodine therapy and 84 Graves’ disease patients treated with radioiodine therapy (1–6 months group [n = 20], 7–12 months group [n = 19], 13–60 months group [n = 29], >60 months group [n = 16]). A and B Show TSAb and TBAb activities in these patients, respectively. The gray circle represents patients with normal levels of TSAb and TBAb; the yellow circle represents patients with high TSAb; the red circle represents patients with high TBAb; the blue circle represents patients with high TSAb and TBAb simultaneously

Fig. 4

Proportion of TSAb- or TBAb-positive patients among GD patients with different thyroid functions after ¹³¹I therapy. A and B Show ratios of TSAb-positive and TBAb-positive patients with Graves’ disease with different thyroid functions after ¹³¹I therapy. *denotes p < 0.01, **denotes p < 0.001