MON-589 Prognostic Predictors of Initial Response of Graves' Disease to Antithyroid Drugs: A Single Center Experience

Prognostic Predictors of Initial Response of Graves’ disease to Antithyroid Drugs: A Single Center Experience Background: Conservative therapy with antithyroid drugs (ATD) is the first-line therapy of Graves' disease (GD) in many areas of the world. Based on the high incidence of relapse after stoppage of ATD, studies were conducted to suggest clinical & laboratory predictors selecting patients most likely to have a remission, this would subject only these patients to the potential risks & inconvenience of ATD. Hence, the aim of our study was to determine the prognostic factors of the initial response of GD six months following initiation of ATD. Subjects & Methods: A single-center prospective study including newly diagnosed patients with GD recruited for 6 months (1st July - 31st December 2017). The studied prognostic factors were: age, sex, goiter size, smoking history, presence of Graves ophthalmopathy, Family history of thyroid disorders, serum TSH, FT3, FT4, FT3:FT4 [ initial, 3 & 6 months after ATD], TRAbs, thyroid volume by US, vascularity & peak systolic velocity of inferior thyroid artery by color Doppler [ initial & 6 months after ATD]. All patients were offered ATD (carbimazole). Patients were followed up for 6 months every 6 weeks with modification of the dose if needed. Patients were subdivided into responders & non-responders after the 6 months period Results: 71 patients with GD; 28 males & 43 females with a mean age of 36.5±10.4 yrs were enrolled. 41% of our patients (29/71) responded to ATD, while 59% (42/71) failed to respond. Euthyroidism was achieved in 15% of pts after 3 months of ATD with almost doubling of this figure after 6 months. In univariate regression analysis; Male gender (p<0.001), current smoking (p=0.001), large pre-treatment goiter size (p = 0.022), high FT3 & FT4 at 3 & 6 months after ATD (p<0.001), high TRAb at baseline (p= 0.03) & 6 months after ATD ( p= 0.002), large total thyroid volume (TV) by US at baseline (p< 0.001) & 6 months after ATD ( p=0.001) and high thyroid vascularity at baseline (p=0.02) are predictors of poor early response to carmbimazole. Serum TRAb at baseline & 6 months after ATD are good predictors for early response to ATD with cut off value ≤ 35 at baseline (86.2 % sensitivity & 42.8 % specificity) & cut off value ≤ 24 after 6 months (93.1% sensitivity, 42.3 % specificity). ROC curves of TV by the US at baseline & 6 months after ATD are good predictors for response to ATD with the cut-off value of 65.5 ml at baseline (83.3% sensitivity, 73.1% specificity) & cut off value ≤15 ml after 6 months (51.7% sensitivity, 97.6% specificity) Conclusions: Patients with GD with large pre-treatment goiter size clinically & by the US, male gender, smokers, high TRAb at baseline & 6 months after ATD, high FT3 & FT4 levels at 3 & 6 months after ATD responded less favorably to initial carbimazole therapy. These finding may help us to sort which patients are better candidates for early definitive therapy.