Changes in Glucose Intolerance after Treatment with Antithyroid Drugs in Patients with Graves' Disease Using Continuous Glucose Monitoring: A Pilot Study

OBJECTIVE: Graves' disease (GD) is known to cause glucose intolerance. The present study used continuous glucose monitoring (CGM) in 15 patients newly diagnosed with GD to evaluate changes in glucose trends following improvement in the thyroid function. METHODS: At the time of the diagnosis of GD, each participant wore a CGM monitor for seven days, and the data recorded on days 3 to 5 were analyzed. The clinical status before treatment with antithyroid drugs was evaluated. Following successful treatment with antithyroid drugs and improvement of free thyroxine (fT4) to within the normal range, CGM was used again to evaluate the same variables after treatment. RESULTS: The primary outcome, the standard deviation (SD) of glucose, improved from a baseline value of 28.9±4.9 to a post-treatment value of 22.2±5.1 mg/dL (p=0.001). Other variables also improved after treatment, including the mean amplitude of glycemic excursion (MAGE), daily average glucose level, nocturnal average glucose level (0:00-05:59), maximum and minimum glucose, percent time with glucose at >140 mg/dL, and percent time with glucose at >180 mg/dL; however, the coefficient of variation (CV) and percent time with glucose at <70 mg/dL did not improve. A univariate analysis showed the significant correlation of the SD with TSH receptor antibody (TRAb) and 1,5-Anhydro-D-Glucitol (1,5-AG). CONCLUSION: Our results showed that CGM-based markers of mean glucose and glucose variability improved with the improvement of the thyroid function in newly diagnosed GD patients treated with antithyroid drugs.