The Prognostic Application of Thyroid Volume Determination in Patients with Graves' Disease

Abstract

Swelling of the thyroid gland is a common symptom in patients with Graves' disease. However, until recently there were no adequate means of measuring the thyroid volume. In this study, thyroid volume (in Graves' disease patients on antithyroid drug (ATD) therapy) was measured serially by a new ultrasound technique involving the use of a specifically programmed computer. The relationships between thyroid volume and prognosis, and between thyroid volume and serum thyroglobulin (Tg) concentration were examined. Sixty untreated patients with Graves' disease and 62 healthy subjects were included in the study. Twenty of the 60 patients with Graves' disease who had no anti-Tg antibodies underwent serial measurement of thyroid volume and serum Tg concentration during long term (18-42 months) ATD therapy. Thyroid volume in normal subjects ranged from 5.6 ml to 20.2 ml, with a mean of 12.0 +/- 4.0 ml. In patients with untreated Graves' disease, the volume ranged from 13.3 to 190.7 ml with a mean of 40.2 +/- 27.8 ml (n = 60). Thyroid volume was significantly correlated with both serum Tg concentration (n = 20, r = 0.678, p less than 0.01) and serum TSH receptor antibody activity (n = 18, r = 0.590, p less than 0.01). During ATD therapy, the thyroid volume decreased gradually in most patients. Eleven of 20 treated patients experienced remission after therapy was discontinued, and in these patients, thyroid volume was significantly smaller (p less than 0.01) than before treatment. Four patients developed hypothyroidism due to over dosage of ATD at which time thyroid volume increased in all four. In the course of therapy, even during episodes of hypothyroidism changes in serum Tg concentrations paralleled changes in thyroid volume. After 12 months of therapy, thyroid volume expressed as a percentage of the pretreatment value was significantly smaller in patients in remission (77.6 +/- 8.9%) than in those who did not show remission (92.4 +/- 11.6%). These data suggest that serial ultrasonographic measurement of thyroid volume is useful in predicting the course of hyperthyroidism in ATD-treated patients with Graves' disease.