Anti-cardiolipin antibodies in autoimmune thyroid diseases

In recent years anti-phospholipid antibodies have gained much attention since they are frequently associated with thrombosis, recurrent abortion, and thrombocytopenia. Besides disease-specific autoantibodies, other autoantibodies reactive with both organ and non-organ specific autoantigens have been found in patients with autoimmune thyroid diseases. Therefore the objective of this study was to evaluate the presence and significance of anti-phospholipid antibodies in untreated patients with different forms of autoimmune thyroid diseases.

Thirty-one patients (26 females, five males; mean age 42.5 years) affected by different autoimmune thyroid diseases were studied. Fourteen patients were affected by Graves' disease, eight by silent thyroiditis, five by Hashimoto's thyroiditis. Four patients with Graves' disease in remission were also evaluated. Anti-cardiolipin antibodies were detected by enzyme linked immunosorbent assay. In five Graves' disease patients anti-cardiolipin antibodies were evaluated before and after 3 months of therapy with methimazole.

Seventeen out of 31 patients were positive for IgG and/or IgM anti-cardiolipin antibodies, the highest levels occurring in three Graves' disease patients with severe thyrotoxicosis. In four of five Graves' patients evaluated before and after methimazole therapy, anticardiolipin antibodies decreased following treatment. None of the patients with increased IgG and/or IgM anticardiolipin antibodies showed clinical manifestations of the anti-phospholipid syndrome during our observation which ranged from 1 to 5 years.

Our results showed an increased incidence of anti-cardiolipin antibodies in patients affected by autoimmune thyroid diseases. However, these autoantibodies seem merely to represent a non-specific marker of immune dysregulation.