Serum immunoglobulin levels in thyroid disease.

Serum levels of IgG, IgA and IgM were assayed by radial immunodiffusion in 261 patients with eight categories of thyroid disease. These composed eighty-three patients with a first episode of untreated active Graves' disease (toxic diffuse goitre), ten with relapsed Graves' disease, seventeen with thyrotoxicosis due to a multinodular goitre, forty-nine with Hashimoto's thyroiditis, twenty-eight with primary (non-goitrous) myxoedema, forty with non-toxic goitre, eighteen with an adenoma and sixteen with euthyroid ophthalmopathy. Eighteen (21·7%) patients with a first episode of Graves' disease had abnormally high IgG levels whereas eight (80%) of those who had relapsed after a course of Carbimazole had high levels. Those Graves' disease patients with raised IgG levels had a significantly higher 24-hr radioiodine uptake than those with normal levels. Eight (16·3%) patients with Hashimoto's thyroiditis had abnormally high levels of IgG associated with a higher incidence of thyroglobulin autoantibodies. Very few (<6%) patients with primary myxoedema, non-toxic goitre and adenoma had abnormal levels. Euthyroid patients with ophthalmopathy had a significantly lower mean IgG level than the corresponding mean level found in the group with active Graves' disease. However, despite the differences between groups described above, there were no significant differences of mean IgG, IgA and IgM levels in seven of the eight groups when compared with normal subjects. Only the group with relapsed Graves' disease had a significantly higher mean IgG. None of the patients studied had abnormal IgM or IgA levels.