Free Thyroxine, Anti-Thyroid Stimulating Hormone Receptor Antibody Titers, and Absence of Goiter Were Associated with Responsiveness to Methimazole in Patients with New Onset Graves' Disease

Abstract

BackgroundAnti-thyroid drug therapy is considered a treatment of choice for Graves' disease; however, treatment response varies among individuals. Although several studies have reported risk factors for relapse after initial treatment, few have assessed responsiveness during the early treatment period. Our study aimed to identify the clinical characteristics for responsiveness to methimazole.MethodsWe included 99 patients diagnosed with Graves' disease for the first time. Drug responsiveness was defined as the correlation coefficients between decreasing rates of free thyroxine level per month and methimazole exposure dose. According to their responsiveness to treatment, the patients were classified into rapid or slow responder groups, and age, sex, free thyroxine level, and thyrotropin binding inhibiting immunoglobulin (TBII) titers were compared between groups.ResultsThe mean patient age was 44.0±13.5 years and 40 patients were male (40%). The mean TBII titer was 36.6±74.4 IU/L, and the mean free thyroxine concentration was 48.9±21.9 pmol/L. The rapid responder group showed higher TBII titer and free thyroxine level at diagnosis, while age, sex, smoking, and presence of goiter did not differ between the two groups. Logistic regression analyses revealed that high level of serum thyroxine, high titer of TBII, and absence of goiter were significantly associated with a rapid response, while age, sex, and smoking were not significant factors for the prediction of responsiveness.ConclusionIn patients with new onset Graves' disease, high level of free thyroxine, high titer of TBII, and absence of goiter were associated with rapid responsiveness to methimazole treatment.

Parameters affecting the period for being euthyroid in newly-diagnosed Graves’ disease treated with antithyroid agent

“…They categorized the response in two groups as 'responding slowly and quickly' and evaluated this period based on various parameters. 8 They revealed that patients with high levels of FT4 and TRab responded more quickly to treatment opposite to our results. On the other hand, there are many studies examining the factors influencing the relapse after medical treatment in patients with GD.…”

“…Some studies have stated that males respond the medical treatment poorer than the females while no gender difference was reported in others alike to our data. 4,[8][9][10] Likewise gender, the effect of age on relapse have conflicting results. For comparison this effect, 40 years of age were generally targeted as we did in our study.…”

“…4,11 Opposite to these findings, no association was observed between age and response or relapse in various works is in agreement with the present study. 8,10,12,13 The relationship between smoking and GD as well as Graves orbitopathy is clearly known. It has been reported that this effect is dose-dependent, more obvious in females, and disappears after several years after quitting smoking.…”

“…8 Although various reports pointed out the effect versus no effect of FT3, FT4 levels and FT3/FT4 ratio individually, some of them examined their effects together. 8,12,15,[19][20][21][22][23] Hussein and his colleagues found that higher FT3 and FT4 levels were correlated with medical treatment failure in a study containing 659 patients which supports our results. 12 Additionally, it has been reported that both pre-treatment low TSH values and TSH suppression which reappear after drug withdrawal were associated with relapse.…”

“…On the contrary, Choi et al revealed that patients with high levels of TRab respond to treatment faster. 8 Furthermore, Genna et al reported that rapid or gradual response to treatment was not affected by TRab and TgAb levels. 28 The presence of TPOAb and TgAb antibodies which are known to be diagnostic markers of Hashimoto's thyroiditis, another autoimmune disease at the other end of the spectrum, are also exist in GD.…”