Thyroid ultrasonography related to clinical and laboratory findings in patients with silent thyroiditis.

We summarized the clinical course of 10 patients with silent thyroiditis and evaluated the clinical usefulness of ultrasonography, in combination with clinical and laboratory findings, for the differentiation from Graves' disease. Serum T3 and T4 were increased in all cases, and the ratio of T3/T4 (ng/micrograms) was 17.8 +/- 3.6 (SD). But in 3 of 10 patients the ratio was greater that 20. TSH receptor antibody (TRAb) and thyroid stimulating antibody (TSAb) were negative in all cases. The estimated thyroid volume by ultrasonography was 18.4 +/- 5.5 ml, which was slightly increased but significantly lower than those in Graves' disease (p less than 0.05). The internal texture of the thyroid showed a decreased echogenicity with a mean echo level of 70.4 +/- 15.4. There was a weak positive correlation between the echo level at the onset of thyrotoxicosis and the lowest T3 level during the clinical course (p less than 0.05). It is suggested that ultrasonography gives a useful information to the diagnosis and outcome of patients with silent thyroiditis.