# Association between anti-nuclear antibody (ANA) positivity and autoimmune thyroid disease markers in a general examination population

## TL;DR

Higher levels of thyroid autoantibodies are linked to increased ANA positivity, suggesting a connection between thyroid and systemic autoimmunity.

## Contribution

First systematic evaluation of ANA positivity and thyroid disease markers in a general population.

## Key findings

- ANA positivity increases with higher TPOAb and TgAb levels in a dose-dependent manner.
- Homogeneous ANA pattern is more common in individuals with high thyroid autoantibodies.
- ANA positivity is more strongly associated with Hashimoto's than Graves' disease markers.

## Abstract

Anti-nuclear antibodies (ANA), key biomarkers in systemic autoimmune diseases (AD), have been reported at higher levels in patients with autoimmune thyroid diseases (AITD), including Hashimoto's thyroiditis (HT) and Graves' disease (GD). However, a systematic evaluation of the association between ANA positivity and AITD serological markers (TPOAb, TgAb, TSH, fT3, fT4) in the general population is lacking.

This retrospective cohort study analyzed data from 7556 individuals undergoing routine health examinations at our hospital. ANA was detected by indirect immunofluorescence. Thyroid markers were measured via chemiluminescence immunoassay. Participants were stratified by predefined clinical cut-offs for each marker. Associations between marker levels and ANA positivity, pattern and titer were analyzed respectively.

ANA positivity rates increased significantly with higher levels of TPOAb (≤34 IU/ml: 6.03 %, 34 IU/ml-100 IU/ml: 13.03 %, ≥100 IU/ml: 16.50 %; P < 0.001) and TgAb levels (≤115 IU/ml: 5.84 %, 115IU/ml-500IU/ml: 18.10 %, ≥500IU/ml: 19.29 %; P < 0.001). Logistic regression confirmed that with the increase in TPOAb and TgAb levels, the positive risk of ANA increased by approximately 1.6-fold and 2.7-fold respectively. TSH ≥4.2 mIU/L showed marginally increased ANA positivity (OR = 1.14, 95 % CI = 0.47–2.75). No significant associations were found with fT3 or fT4. AC-4/5 (speckled, 37.64 %) and AC-1 (homogeneous, 27.95 %) were dominant ANA patterns; the AC-1 prevalence increased with higher TPOAb/TgAb levels.

Elevated thyroid autoantibodies (TPOAb, TgAb) are strongly associated with increased ANA positivity risk, suggesting a link between thyroid-specific and systemic autoimmunity. Thyroid hormone levels showed minimal association. Patients with high TPOAb/TgAb, especially females, may benefit from ANA screening.

•ANA positivity is dose-dependently linked to high TPOAb/TgAb.•ANA is associated with elevated TSH, suggesting hypothyroidism risk.•Homogeneous ANA pattern predominates in high-thyroid-antibody cases.•ANA links specifically to Hashimoto's, not Graves' disease, markers.

ANA positivity is dose-dependently linked to high TPOAb/TgAb.

ANA is associated with elevated TSH, suggesting hypothyroidism risk.

Homogeneous ANA pattern predominates in high-thyroid-antibody cases.

ANA links specifically to Hashimoto's, not Graves' disease, markers.