Toxic Multinodular Goiter: A Variant of Autoimmune Hyperthyroidism*

The aim of this study was to examine whether at least a subgroup of patients with toxic multinodular goiter may have autoimmune thyroid disease. Thyroid-stimulating immunoglobulin (TSI) activity, measured by a sensitive bioassay employing cultured human thyroid cells, was determined in patients with toxic multinodular goiter and other thyroid disorders. All patients with active Graves' disease (n = 47) had detectable serum TSI activity, whereas TSI was undetectable in patients with thyroid disease not believed to be of autoimmune origin: toxic adenoma (n = 13), cold nodule (n = 5), and nontoxic goiter (n = 19), with a single exception in the latter group. Toxic multinodular goiter (n = 26) was diagnosed based on clinical and laboratory evidence of hyperthyroidism associated with a multinodular goiter on palpation and scintiscan. The toxic multinodular goiter group was then subclassified according to scintiscan pattern (type A, diffuse but uneven distribution of technetium uptake; type B, multiple discrete...