Autoantibodies against complement C1q correlate with the thyroid function in patients with autoimmune thyroid disease

Clin Exp Immunol. 2008 Jul;153(1):96-101. doi: 10.1111/j.1365-2249.2008.03670.x. Epub 2008 May 23.


Autoantibodies against complement C1q (anti-C1q) have been well described in patients with systemic lupus erythematosus, where they correlate with the occurrence of severe lupus nephritis. However, data on anti-C1q in organ-specific autoimmune diseases are scarce. In order to determine the prevalence of anti-C1q in patients with autoimmune thyroid disorders (AITD) and a possible association with thyroid function, we measured prospectively anti-C1q in 23 patients with Graves' disease (GD) and 52 patients with Hashimoto's thyroiditis (HT). Anti-C1q levels were correlated with parameters of thyroid function and autoantibodies against thyroperoxidase, thyroglobulin and thyroid stimulating hormone (TSH) receptor. Twenty-one patients with multi-nodular goitre and 72 normal blood donors served as controls. We found elevated concentrations of anti-C1q more frequently in patients with AITD than in controls: seven of 23 (30%) patients with GD and 11 of 52 (21%) patients with HT, compared with one of 21 (5%) patients with multi-nodular goitre and six of 72 (8%) normal controls. Anti-C1q levels did not correlate with thyroid autoantibodies. However, in GD absolute levels of anti-C1q correlated negatively with TSH and positively with free thyroxine (FT4) and triiodothyronine (FT3). In contrast, in HT, anti-C1q correlated positively with TSH levels. No correlation between TSH and thyroid autoantibodies was found. In conclusion, we found an increased prevalence of anti-C1q in patients with AITD and their levels correlated with the thyroid function in both GD and HT. This correlation seems to be independent of thyroid autoantibodies. Therefore, anti-C1q might point to a pathogenic mechanism involved in the development of AITD that is independent of classical thyroid autoantibodies.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acute Disease
  • Aged
  • Autoantibodies / blood*
  • Case-Control Studies
  • Chi-Square Distribution
  • Complement C1q / immunology*
  • Female
  • Goiter / immunology
  • Graves Disease / immunology*
  • Graves Disease / physiopathology
  • Hashimoto Disease / immunology*
  • Hashimoto Disease / physiopathology
  • Humans
  • Male
  • Middle Aged
  • Prospective Studies
  • Thyroid Function Tests
  • Thyroid Gland / physiopathology


  • Autoantibodies
  • Complement C1q