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

Abstract

Objective: Measurement 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 methods: ITA-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.

Results: ITA-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+/-2103.7mm(3), 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.

Conclusion: Monthly measurement of ITA-PSV after delivery in remitted euthyroid women with GD may assist in early prediction of GD relapse.