Abstract 74: Utility of inferior thyroid artery blood flow velocities to differentiate between gestational transient thyrotoxicosis and Graves’ disease in pregnancy – A pilot study

Background: Thyrotoxicosis is seen in up to 0.1% to 0.5% of pregnancies. Thyrotoxicosis mimics common physiologic changes in pregnancy leading to difficulty in diagnosis. Role of thyroid blood flow velocities to differentiate between Graves disease (GD) and gestational transient thyrotoxicosis (GTT) is not well explored. Aims: To determine the role of inferior thyroid artery- blood flow velocities, assessed by colour-flow Doppler ultrasonography to differentiate between GTT and GD in pregnancy. Methodology: The present cross-sectional study, conducted at Department of Endocrinology, Gandhi Medical College, for a duration of 6 months. 28 subjects participated in the study - 8 with GD and 10 with GTT and 10 Euthyroid pregnant women. The inferior thyroid artery- peak systolic velocity (ITA-PSV) and end-diastolic velocity (EDV) of both right and left sides were evaluated using color doppler ultrasonography. Results: The ITA-PSV and EDV in patients with GTT were significantly lower than those of pregnant patients with GD and significantly higher than those in euthyroid pregnant women. The most appropriate cut off values were obtained by the ROC curve. The optimal cut-off points of ITA-PSV to differentiate between GTT and GD, was 34.5 cm/s, with sensitivity and specificity of 83.42% and 92.43% respectively. Conclusion: Thus ITA-PSV appears to provide excellent sensitivity and specificity to differentiate between GD and GTT, where thyroid scintigraphy is contraindicated.