Hyperthyroidism in Tasmania following iodide supplementation: measurements of thyroid-stimulating autoantibodies and thyrotropin.

Abstract

Serum thyroid-stimulating autoantibodies (LATS and LATS protector) and thyrotropin (TSH) concentrations were measured in the serum of 30 patients with hyperthyroidism living in Tasmania who developed their disease following correction of iodine deficiency by addition of iodate to the bread. Patients were grouped according to thyroid scan results. None of 8 patients with autonomous thyroid nodules had thyroid-stimulating autoantibodies. These were present in both of the patients with uniform thyroid scans and 14 of 20 patients (70%) with irregular scans without demonstrated localized autonomy. Serum TSH, measured by immunoassay of concentrated serum extracts, was 0.15 muU/ml or less in all patients, below the range of 0.35 to 2.60 muU/ml found in normal subjects. Only 6 (20%) of the 30 patients failed to show either localized autonomy or thyroid-stimulating autoantibodies. In most regards these patients resembled those with antonomous nodules. The findings support the conclusion that the increased incidence of phyerthyroidism in Tasmania was due to an increased supply of iodine to patients with latent hyperthyroidism whose thyroid glands, due to the presence of toxid nodule(s) or thyroid-stimulating autoantibodies, were unresponsive to control by TSH deprivation. There was no evidence for additional pathogenic mechanisms