An elevation of serum immunoglobulin E provides a new aspect of hyperthyroid Graves' disease.

Abstract

In hyperthyroid Graves' disease, short-term methimazole is sufficient to induce lasting remission in some patients, but even long-term treatment fails to do so in others. We have evaluated the role of autoimmune abnormalities in the helper T cell type 2 (TH2)-interleukin-13 (IL-13)-TSH receptor system in maintaining hyperthyroidism by comparing IgE levels in patients with various thyroid diseases. One hundred and ninety-three patients with hyperthyroid Graves' disease were treated with methimazole, and blood samples were obtained to measure serum levels of T4, T3, TSH, thyroglobulin, antimicrosomal antibody, TSH binding inhibitory Ig (TBII), thyroid-stimulating antibody, thyroid stimulation-blocking antibody, IgE, interferon-gamma, IL-4, and IL-13. Elevation of serum IgE (> or = 170 U/mL) was found in 35.5% of patients with hyperthyroid Graves' disease, and serum levels of T4, T:1, antimicrosomal antibody, and TBII were significantly greater in patients with IgE elevation than in those with normal serum IgE. During methimazole treatment, there was a parallel decrease in the serum T4 concentration in the presence or absence of an IgE elevation. However, there was a significantly smaller decrease in TBII in patients with elevated IgE than in those with normal IgE. As a result, the remission rate was significantly greater in patients with normal IgE than in those with IgE elevation. Serum levels of IL-13 were elevated in 64.7% of patients with IgE elevation in the absence of detectable TH1 marker, interferon-gamma. These findings suggest that in one third of patients with hyperthyroid Graves' disease, TH2 cells are stimulated and secrete excess amounts of IL-13, which subsequently stimulates B cells to synthesize more TSH receptor antibody and IgE, so that during methimazole treatment TBII decreases less in patients with IgE elevation, producing a lower remission rate.