SAT-423 Anti-thyroid Drug Response in Graves’ Disease: Predictors of Biochemically Persistent Disease

Introduction: Anti-thyroid Drugs (ATD) have become the most frequently used treatment for Graves’ disease (GD) in the United States. However, the response to this therapy is variable. Factors that predict biochemically responsive vs. biochemically persistent disease remain unknown. Identifying predictors of disease poorly responsive to ATD can help guide treatment decision making, follow up planning and prognosis. Methods: From a database of patients with GD treated with ATD and receiving care at an academic medical center between 2009–2019, we selected adults with incident GD treated with ≥14 days of ATD. Results: 172 patients (from a database of 730 patients with GD on ATD) were sampled for the purpose of this pilot and 97 of these met inclusion criteria. Patients had a median age of 50 (18–90); female, 70.1%; never smokers, 64.9%; median goiter size of 40 g (15–100); and median TRAb on presentation of 8.1 mIU/L (1.0- 60). Graves’ orbitopathy (GO) was present in 13.4% at baseline. Patients (100%) were started on methimazole at a median dose of 20 mg (2.5–60). The median time from presentation until biochemical improvement (defined as the first instance of FT4 ≤1.7 ng/dL) was 120.9 days (18–1525), and to biochemical euthyroidism (normal TSH & FT4) was 251 days (41–1259) including a median of 3 (0–17) dose adjustments. In a univariate analysis, response to ATD was divided into two groups; biochemically responsive and biochemically persistent disease (based on reaching biochemical improvement in ≤6 months, or >6 months respectively). Biochemically persistent disease was more common in those with GO at presentation (38.5% vs.11.1%) (p .024). There was a trend towards greater prevalence of biochemically persistent disease in those with TRAb ≥ 8.0 mIU/L (46.2% vs. 27.8%) (p .204), and goiter estimated 30 grams or above by physical examination (30.8% vs. 19.4%) (p .460). Biochemically responsive disease was associated with higher frequency of hypothyroidism during treatment (p .047). Conclusion: Our preliminary results illustrate the spectrum of response to ATD and predictors of biochemically persistent disease. We aim to expand this analysis utilizing a large database. As use of ATD increases, clinicians and patients can apply this data to estimate response to therapy, and identify patients that may require more aggressive therapy, thereby tailoring management plans.