Anti‐cardiolipin antibodies in autoimmune thyroid diseases

Abstract

Summary OBJECTIVE 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. PATIENTS AND METHODS 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. RESULTS 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, anti‐cardiolipin antibodies decreased following treatment. None of the patients with increased IgG and/or IgM anti‐cardiolipin antibodies showed clinical manifestations of the anti‐phospholipid syndrome during our observation which ranged from 1 to 5 years. CONCLUSIONS 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.

Thyroid-associated autoimmune coagulation disorders

“…Paggi et al found antiphospholipid antibodies in 17 of 31 patients (55%) with autoimmune thyroid diseases. The antibody titer was highest in patients with Graves' disease and decreased with methimazole treatment [47]. Likewise, Marongiu et al [52] found an increased incidence of antiphospholipid antibody positivity in Graves' disease patients compared to healthy controls (38% vs. 0%).…”

“…A number of case reports and small case series have documented the close link between antiphospholipid antibodies and autoimmune thyroid disorders [47][48][49][50][51][52][53][54][55]. A crossreactivity between b 2 -GPI and epitopes of thyrotropin receptor has been hypothesized as a pathogenic mechanism explaining the association between these two autoimmune conditions [56].…”

Hemostatic abnormalities in endocrine and metabolic disorders

“…For example, it is known that there is a biological link between antiphospholipid antibodies and Graves' disease (49)(50)(51)(52)(53). Moreover, Homoncik et al found increased plasma VWF levels and enhanced platelet function (as measured with PFA-100 analyzer) in patients with hyperthyroidism compared with euthyroid controls (54).…”

Choreathetosis due to abuse of levothyroxine

“…Dopamine receptor sensitivity is indeed increased in experimental thyrotoxic chorea [8]. The anticardiolipin antibodies, which in our patient with autoimmune thyroiditis probably were immunological epiphenomena [9], may yet have had a facilitating effect. Also, the history of vocal tics during childhood may point towards a genetic predisposition for involuntary movements.…”