HIGH THYROPEROXIDASE ANTIBODY TITERS MAY PREDICT RESPONSE TO ANTITHYROID DRUG TREATMENT IN GRAVES DISEASE: A PRELIMINARY STUDY.

Abstract

Antithyroid drugs are first treatment for Graves hyperthyroidism worldwide. Although remission can be achieved in approximately 40-50% of patients in 12-18 months with antithyroid drugs, this period can be extended up to 24 months. We aimed to evaluate the effect of individual clinical/biochemical variables and GREAT score in predicting response to antithyroid drug in Graves disease. This is a retrospective single-center study including 99 patients with the first episode of Graves disease treated for at least 18 months. The patients were classified into two groups as those who responded to antithyroid medication at 18-24 months (group 1) and those who did not respond at 24 months and continued with low-dose antithyroid medication (group 2). Medical treatment response was obtained in 38 (38.3%) of the patients at 18 months, and in 19 (19.1%) patients at 24 months. Long-term medical treatment (>24 months) was given to the remaining 43 patients due to the lack of response to medical treatment. Thyroid volume and free T4 levels were higher in those followed up with long-term antithyroid drugs, and orbitopathy was more common in this group. Median anti TPO value was significantly higher in group 1 when compared to group 2 (593 U/l and 191.6 U/l respectively). More patients were classified as GREAT class 3 in group 2 when compared to group 1 (46.5% and 12,5% respectively). We analyzed the Thyroperoxidase Antibody(anti TPO) titers, which we divided into three levels, according to groups 1 and 2. Post-hoc Chi-Square analysis revealed that falling into the highest anti TPO category was significantly associated with response to medical therapy in 24 months (p <0.05). According to our study, GREAT score and anti TPO Ab titers at presentation may help predict response to ATD in Graves disease.