Thyroid blood flow as a useful predictor of relapse of Graves’ disease after normal delivery in patients with Graves’ disease

ObjectiveMeasurement of the peak systolic velocity (PSV) in the inferior thyroid artery (ITA) before withdrawal of an anti-thyroid drug (ATD) is useful for predicting relapse of Graves’ disease (GD). We further investigated whether the ITA–PSV can be used for prediction of GD relapse after delivery in euthyroid women with GD who stopped ATD administration during mid- to late pregnancy.Patients and methodsITA–PSV was monitored monthly for three months after delivery in 42 women with GD aged from 24 to 45 years old (mean ± SE: 34.7 ± 0.92 years old) who met the above criteria. To confirm the stability of the measurement, ITA–PSV was also measured monthly in 32 age-matched non-pregnant normal women and for three months after delivery in 10 age-matched women.ResultsITA–PSV and thyroid volume were higher in women with GD immediately after delivery compared to normal women, but the levels of TSH receptor antibody (TRAb) and thyroid-stimulating antibody (TSAb) did not differ significantly between the two groups. Of the 42 patients, 23 had relapse of GD and the smoker/non-smoker ratio and thyroid volume in these patients immediately after delivery were significantly higher than those in the 19 patients who did not undergo relapse (10/23 vs. 0/19, p < 0.0001; 24280.3 ± 2280.9 vs. 19670.0 ± 2103.7 mm3, p = 0.046), while ITA–PSV, TRAb and TSAb did not differ between the two groups of patients. The ITA–PSV ratio was calculated by dividing each value in the follow-up period by that obtained immediately after delivery. A significant increase in the mean ITA–PSV ratio occurred at least one month before the time of relapse (1.00 ± 0.00 at –3 months before relapse vs. 1.46 ± 0.12 at –1 month, p = 0.010; 1.00 ± 0.00 at –3 months vs. 1.77 ± 0.13 at the time of relapse, p = 0.0048). In contrast, there were no significant changes in this ratio during the follow-up period in non-relapse patients.ConclusionMonthly measurement of ITA–PSV after delivery in remitted euthyroid women with GD may assist in early prediction of GD relapse.