The Basal Thyroid Hormones Level and Antithyroid Drugs Responsiveness in Graves’ Disease

Introduction: Graves’ disease (GD) is the most common cause of hyperthyroidism worldwide. Antithyroid drugs are considered as the first line of treatment in many countries. However, there are wide variations in the dose, regimen or duration of treatment, this is not exactly clear which factor is more important in drug responsiveness. The aim of this study was to evaluate the effect of basal levels of thyroid hormones in response to antithyroid drug therapy (ADT).Materials & Methods: In this cross-sectional study, the patients with Graves’ disease were enrolled. The data of weight, body mass index (BMI), and level of thyroid hormones in basal state and three months after antithyroid drug therapy were extracted from the patients’ medical records. The delta change of the variables was calculated after three months and their correlation with basal thyroid hormone levels was evaluated.Results: Ninety one Graves disease patients (95% female) were enrolled in the study. The mean age of patients was 34.1±13.8 years .The level of basal thyroid hormones T3, T4, TSH was 3.9±1.95 ng/dl, 20.28 ±6.50 µg/dl and 0.096 ± 0.11mIu/ml respectively. The higher basal level of T3 was significantly correlated with decrease in T3 level after three months antithyroid therapy (r=o.84, P=0.000) but there was not a significant change in the TSH level, weight, and BMI in basal and after treatment states. Also, the basal level of T4 had a positive correlation with delta change in the T4 level (r=o.80, P=0.000). Conclusion: According to the results of our study, the higher basal thyroid hormone level correlates with better response to antithyroid drugs.