Endocrine Abstracts

Background: The acitivity of the TSH receptor stimulating antibody is known to be associated with Graves’ eye disease. However, the association between antibody titer and thyroid function was not significant, in previous studies. Taking into account the continuous changes in antibody titer and thyroid function during treatment, the association between thyroid function and clinical factors needed to be analyzed using panel analysis.

Methods: A total of 210 patients who visited and were treated in a tertiary hospital between 1999 February and 2019 May were included in this study. The patients were treated with methimazole according to their thyroid function status. Thyroid function test and thyrotropin binding inhibitor immunoglobulin (TBII) titer were measured at regular visit. We excluded patients who had relapsed after remission or underwent surgery or radioactive iodine treatment. Because the distribution of TBII was right skewed, TBII titer was transformed to base-10 logarithm. We performed panel analysis to evaluate the effect of factors on free T4 level during treatment period.

Results: The mean age of the patients was 43.4±14.5, male patients were 86 (40.9%) and females were 124 (59.1%). At first diagnosis, mean of free T4 was 3.46±1.83 ng/dL, and median of TBII was 10.2 (IQR: 5~23.99). The dose of methimazole at the time of diagnosis was 18.5±10 mg a day. In the panel analysis for the free T4 level, the patient’s age showed a negative association (Coef [95% CI] = -0.007 [-0.010 - -0.004]), and TBII showed a positive association (Coef [95% CI] = 0.272 [0.227 – 0.317]). However, sex and dose of methimazole did not show significant association with free T4 level.

Conclusion: In this study, we observed the positive association between TBII titers and free T4 levels in panel analysis. In the future, further studies using long-term follow-up clinical data are warranted to find associated factors for clinical course of Graves‘ disase.