Relationship of Anti-TPO antibody levels with hematologic inflammation indices in hashimoto’s thyroiditis

Aim: This study aimed to evaluate the relationship between anti-thyroid peroxidase antibody (anti-TPO) levels and hematological markers of systemic inflammation — including the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), monocyte-to-lymphocyte ratio (MLR), and systemic immune-inflammation index (SII) in treatment-naïve patients with Hashimoto’s thyroiditis (HT).

Materials and Methods: This retrospective, cross-sectional study included 416 newly diagnosed, treatment-naïve HT patients. Participants were categorized into low (n=208) and high (n=208) anti-TPO groups based on the median anti-TPO value (208 IU/mL). Thyroid function tests and complete blood count parameters were analyzed, and NLR, PLR, MLR, and SII were calculated. Spearman’s correlation and multivariable linear regression analyses were performed.

Results: The high anti-TPO group had significantly higher TSH [5.87 (3.60–10.07) vs. 4.14 (2.62–6.60) µIU/mL; p<0.001] and lower fT4 levels [0.75 (0.64–0.86) vs. 0.80 (0.70–0.90) ng/dL; p=0.001] compared with the low group. Anti-TPO correlated positively with TSH (ρ=0.248; p<0.001) and negatively with fT4 (ρ=−0.185; p<0.001). PLR was significantly lower in the high anti-TPO group [113 (92.3–146) vs. 122 (97–155); p=0.025]. However, no significant correlations or independent associations were found between anti-TPO and NLR, MLR, or SII in regression analysis (model R²=0.015; p=0.190). Although PLR differed between groups, it was not an independent predictor of anti-TPO after adjustment. The low R2 suggests a biological dissociation between local autoimmunity and systemic inflammation.

Conclusion: Anti-TPO levels were not significantly associated with hematologic inflammatory markers in treatment-naïve HT. These findings suggest that, in early-stage HT, local autoimmune activation may occur independently of systemic inflammation and that hematologic indices may have limited clinical utility for early diagnosis or disease monitoring.