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

Enhanced predictive validity of integrative models for refractory hyperthyroidism considering baseline and early therapy characteristics: a prospective cohort study

BACKGROUND

A subset of Graves' disease (GD) patients develops refractory hyperthyroidism, posing challenges in treatment decisions. The predictive value of baseline characteristics and early therapy indicators in identifying high risk individuals is an area worth exploration.

METHODS

A prospective cohort study (2018-2022) involved 597 newly diagnosed adult GD patients undergoing methimazole (MMI) treatment. Baseline characteristics and 3-month therapy parameters were utilized to develop predictive models for refractory GD, considering antithyroid drug (ATD) dosage regimens.

RESULTS

Among 346 patients analyzed, 49.7% developed ATD-refractory GD, marked by recurrence and sustained Thyrotropin Receptor Antibody (TRAb) positivity. Key baseline factors, including younger age, Graves' ophthalmopathy (GO), larger goiter size, and higher initial free triiodothyronine (fT3), free thyroxine (fT4), and TRAb levels, were all significantly associated with an increased risk of refractory GD, forming the baseline predictive model (Model A). Subsequent analysis based on MMI cumulative dosage at 3 months resulted in two subgroups: a high cumulative dosage group (average ≥ 20 mg/day) and a medium-low cumulative dosage group (average < 20 mg/day). Absolute values, percentage changes, and cumulative values of thyroid function and autoantibodies at 3 months were analyzed. Two combined predictive models, Model B (high cumulative dosage) and Model C (medium-low cumulative dosage), were developed based on stepwise regression and multivariate analysis, incorporating additional 3-month parameters beyond the baseline. In both groups, these combined models outperformed the baseline model in terms of discriminative ability (measured by AUC), concordance with actual outcomes (66.2% comprehensive improvement), and risk classification accuracy (especially for Class I and II patients with baseline predictive risk < 71%). The reliability of the above models was confirmed through additional analysis using random forests. This study also explored ATD dosage regimens, revealing differences in refractory outcomes between predicted risk groups. However, adjusting MMI dosage after early risk assessment did not conclusively improve the prognosis of refractory GD.

CONCLUSION

Integrating baseline and early therapy characteristics enhances the predictive capability for refractory GD outcomes. The study provides valuable insights into refining risk assessment and guiding personalized treatment decisions for GD patients.

Clinical efficacy of thyroid-stimulating immunoglobulin detection for diagnosing Graves' disease and predictors of responsiveness to methimazole

BACKGROUND

As thyroid-stimulating immunoglobulins (TSI) are a sign of Graves' disease (GD), measuring TSI titers is becoming increasingly important for GD diagnosis. This study evaluated the diagnostic accuracy of a new fully automated TSI immunoassay (Immulite™ TSI assay) in GD patients and compared it to the third generation thyroid-stimulating hormone receptor antibody (TRAb) electrochemiluminescence assay (Elecsys Anti-TSHR assay). Additionally, clinical characteristics associated with responsiveness to methimazole in patients with newly diagnosed GD were preliminarily explored.

METHODS

This study involved 324 subjects, comprising patients with untreated GD (GD-UT), Graves' ophthalmopathy (GO) patients, GD patients who had been treated for > 12 months (GD-T), autoimmune thyroiditis (AIT) patients, and healthy subjects (HS). The Immulite™ TSI and Elecsys Anti-TSHR assay were performed on all samples. According to their responsiveness to methimazole, the GD-UT patients were divided into rapid and slow responder groups, and their clinical characteristics were compared.

RESULTS

A receiver operating characteristic (ROC) curve analysis of GD-UT patients showed that the optimal TSI cut-off value was 0.57 IU/L. Logistic regression revealed that age and initial FT4 and TSI levels in the middle-dose methimazole group were related to a rapid response, while the initial FT4 level, but not TSI, in the high-dose group was also associated with a rapid response.

CONCLUSIONS

The clinical diagnostic performance of the Immulite™ TSI assay for diagnosing GD was comparable to that of the Elecsys Anti-TSHR assay. The initial FT4 and TSI levels can be used as predictors of the responsiveness to methimazole in patients with newly diagnosed GD.

Agoitrous Graves' Hyperthyroidism with Markedly Elevated Thyroid Stimulating Immunoglobulin Titre displaying Rapid Response to Carbimazole with Discordant Thyroid Function

We characterize the clinical and laboratory characteristics of 5 patients with Graves’ thyrotoxicosis whose serum free thyroxine (fT4) concentration decreased unexpectedly to low levels on conventional doses of carbimazole (CMZ) therapy. The initial fT4 mean was 40.0 pM, range 25–69 pM. Thyroid volume by ultrasound measured as mean 11 ml, range 9.0–15.6 ml. Initial TSI levels measured 1487% to >4444%. Serum fT4 fell to low-normal or hypothyroid levels within 3.6 to 9.3 weeks of initiating CMZ 5 to 15 mg daily, and subsequently modulated by fine dosage adjustments. In one patient, serum fT4 fluctuated in a “yo-yo” pattern. There also emerged a pattern of low normal/low serum fT4 levels associated with discordant low/mid normal serum TSH levels respectively, at normal serum fT3 levels. The long-term daily-averaged CMZ maintenance dose ranged from 0.7 mg to 3.2 mg. Patients with newly diagnosed Graves’ hyperthyroidism who have small thyroid glands and markedly elevated TSI titres appear to be “ATD dose sensitive.” Their TFT on ATD therapy may display a “central hypothyroid” pattern. We suggest finer CMZ dose titration at closer follow-up intervals to achieve biochemical euthyroidism.

Changes in Thyroid Peroxidase and Thyroglobulin Antibodies Might Be Associated with Graves' Disease Relapse after Antithyroid Drug Therapy

BACKGROUND

Graves' disease (GD) is an autoimmune thyroid disorder caused by antibodies stimulating the thyrotropin (TSH) receptor. TSH receptor antibody (TRAb) measurement is useful for predicting GD relapse after antithyroid drug (ATD) treatment. However, the association of other thyroid autoantibodies with GD relapse remains obscure.

METHODS

This retrospective study enrolled patients with GD who were initially treated with ATD. TRAb, thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb) were measured at the initial diagnosis and at the time of ATD discontinuation.

RESULTS

A total of 55 patients were enrolled. The mean age was 49.7 years, and 39 patients (70.9%) were female. Antibody positivity at diagnosis was 90.9%, 69.1%, and 61.9% for TRAb, TPOAb, TgAb, respectively. Median ATD treatment period was 15.1 months. At the time of ATD withdrawal, TRAb titers decreased uniformly overall. Conversely, TPOAb and TgAb showed various changes. After withdrawal of ATD, 19 patients (34.5%) experienced relapse. No clinical features or laboratory results were significantly related to relapse in the overall patient group. However, in the TPOAb positive group at diagnosis, increasing titer of TPOAb or TgAb after ATD treatment was significantly and independently related to relapse free survival (TPOAb: hazard ratio [HR], 17.99; 95% confidence interval [CI], 1.66 to 195.43; P=0.02) (TgAb: HR, 5.73; 95% CI, 1.21 to 27.26; P=0.03).

CONCLUSION

Changes in TPOAb or TgAb titers during treatment might be useful for predicting relapse after ATD treatment in patients with positive TPOAb at diagnosis.

When should antithyroid drug therapy to reduce the relapse rate of hyperthyroidism in Graves' disease be discontinued?

OBJECTIVE

The use of antithyroid drug (ATD) therapy in patients with Graves' disease (GD) hyperthyroidism has been increasing, but ATD therapy is associated with a higher relapse rate. We aimed to evaluate clinical factors for predicting relapse of GD after ATD therapy.

METHODS

Patients (n = 149) with newly diagnosed GD who achieved remission of hyperthyroidism after ATD therapy (≥6 months) were followed up for >18 months after ATD withdrawal. We evaluated the predictive factors of relapse during a median of 6.9 years of follow-up.

RESULTS

Disease relapse occurred in 52 patients (34.9%). By multivariate analyses, a duration of the minimum maintenance dose therapy (MMDT) of <6 months was a significant factor in disease relapse (hazard ratio [HR], 2.58; 95% confidence interval [CI], 1.47-4.52; p < 0.001), and a T3/free T4 (fT4) ratio > 120 at ATD withdrawal was significantly more frequent in patients with relapse (HR 2.43; 95% CI, 1.36-4.34; p = 0.002). In the prediction-of-relapse model, the likelihood of relapse was greater in the high-risk group, which had a short MMDT duration and a T3/fT4 ratio ≥120 (HR, 5.81; 95% CI, 2.52-13.39; p < 0.001) and the intermediate-risk group, which had a short MMDT duration or a T3/fT4 ratio < 120 (HR, 2.77; 95% CI, 1.26-6.13; p < 0.001), than in the low-risk group, which had a long MMDT duration and a T3/fT4 ratio < 120.

CONCLUSION

An MMDT longer than 6 months and a high T3/fT4 ratio at ATD withdrawal were independent predictors of relapse in patients who achieved initial remission after ATD for GD. These factors could be used to determine the optimal time to withdraw ATD during the treatment of GD hyperthyroidism.