Circulating immune complexes in various thyroid diseases.

In a study of 171 patients with various thyroid diseases, circulating immune complexes (CIC), measured by a C1q solid phase radioassay, were detected in 26% of the patients as compared to 8% of the control subjects. CIC were found in 33--55% of the patients with a well defined thyroid autoimmune disorder (Hashimoto's goitre, asymptomatic thyroiditis, spontaneous myxoedema and Graves' disease) and also in the same proportion of patients with diffuse goitre. CIC were correlated to the presence of serum antibodies to microsomal thyroid antigen but not to their titre. No relationship was observed between CIC and the age or sex of the patients and the presence of exophthalmos, or between CIC and the different thyroid function tests or serum anti-thyroglobulin antibodies. CIC were found in untreated patients as well as in those treated with prednisone, methimazole or thyroxine.