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

Area of Science:

• Immunology
• Endocrinology
• Autoimmunity

Background:

• Autoantibodies against complement C1q (anti-C1q) are linked to lupus nephritis in systemic lupus erythematosus.
• Data on anti-C1q in organ-specific autoimmune diseases, like autoimmune thyroid disorders (AITD), are limited.
• Understanding anti-C1q's role in AITD may reveal new pathogenic mechanisms.

Purpose of the Study:

• To determine the prevalence of anti-C1q in patients with Graves' disease (GD) and Hashimoto's thyroiditis (HT).
• To investigate the association between anti-C1q levels and thyroid function parameters in AITD.
• To explore the relationship between anti-C1q and thyroid autoantibodies.

Main Methods:

• Prospective measurement of anti-C1q in 23 GD patients, 52 HT patients, 21 multi-nodular goitre controls, and 72 healthy controls.
• Correlation analysis of anti-C1q levels with thyroid function tests (TSH, FT4, FT3) and thyroid autoantibodies (TPOAb, TgAb, TRAb).
• Comparison of anti-C1q prevalence between patient groups and controls.

Main Results:

• Elevated anti-C1q was found more frequently in AITD patients (30% GD, 21% HT) than in controls (5% MNG, 8% healthy).
• Anti-C1q levels did not correlate with thyroid autoantibodies.
• In GD, anti-C1q correlated negatively with TSH and positively with FT4 and FT3. In HT, anti-C1q correlated positively with TSH.

Conclusions:

• Anti-C1q is more prevalent in patients with autoimmune thyroid disorders.
• Anti-C1q levels correlate with thyroid function in both Graves' disease and Hashimoto's thyroiditis.
• These correlations are independent of classical thyroid autoantibodies, suggesting a distinct pathogenic role for anti-C1q in AITD.