SUMMARY
Objective: Graves’ disease and Hashimoto’s thyroiditis are the most common causes of hyper and hypothyroidism, respectively. Differentiation of these 2 diseases, if the patient is euthyroid, may sometimes be extremely difficult on the basis of clinical and laboratory findings. The purpose of this study was to determine the sensitivity and specificity of gray scale sonography in differentiation of Graves’ disease from Hashimoto’s thyroiditis. Methods: This study included 149 patients divided into three groups, patients with Graves’ disease (34 patients, mean age = 36.8 ± 10.17 years), Patients with Hashimoto’s thyroiditis (62 patients, mean age = 33.4 ± 12.16 years) and control group (53 healthy people, mean age = 34.74 ± 16.87 years). Members of all groups were referred to a single radiologist for thyroid sonography for evaluation of thyroid echogenicity pattern. Results: A total of 117 women and 32 men were examined by sonography. The most common sonographic pattern in Hashimoto and Graves’ was homogenous hypo-echogenicity which was observed in 45.2% and 47.1% of cases, respectively. Peripheral hypo-echogenicity pattern was seen in 40.3% of Hashimoto’s group with 100% specificity and 40.3% sensitivity. Central-hypoechogenic pattern was observed in 17.6% of Graves’ group with 100% and 17.6% specificity and sensitivity, respectively.Conclusion: Our findings indicate that sonography has high specificity but low sensitivity in the diagnosis of either Graves’ disease or Hashimoto’s thyroiditis. It is therefore not possible to differentiate between these two diseases using sonography alone. Confirmation by laboratory data is also needed.