Endocrine Abstracts

Objective: Previous studies have suggested that increased thyroid peroxidase antibody (TPOAb) levels are a low-grade inflammatory marker. However, limited research has investigated its association with high-sensitivity C-reactive protein (hs-CRP). We aimed to explore the association between TPOAb levels and elevated hs-CRP levels in men and women, using data from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil).

Methods: We included participants with information on hs-CRP, TPOAb, and covariates, hs-CRP < 10 mg/l; and, without previous cardiovascular disease or stroke (n = 5,476 men, 51.5±9.1 years old; n = 6,575 women, 51.7±8.8 years old). Fasting serum levels of hs-CRP and TPOAb were measured. Elevated hs-CRP was defined as values between 3 and 10 mg/l. TPOAb was categorized as undetectable (≤5.00 IU/ml), low detectable (5.01-14.99 IU/ml), high detectable (15.00-33.99 IU/ml), and positive (≥34.00 IU/ml). Logistic regression models assessed hs-CRP as the dependent variable (reference: not elevated) and TPOAb as the independent variable (reference: undetectable). Univariate and adjusted models (Model 1 adjusted for sex, age, race, log-TSH and log-FT4 levels; Model 2 adjusted for model 1 plus diabetes, hypertension, dyslipidemia, smoking, eGFR< <60 ml/min/1.73 m² and BMI≥30 kg/m²) were performed. For the sensitivity analysis, we excluded individuals (181 men and 819 women) with clinical thyroid diseases.

Results: The prevalence of elevated hs-CRP levels was 19.6% and 27.9% for men and women, respectively (chi-square test, P < 0.001). Men with low and high TPOAb detectability were more likely to have elevated hs-CRP than the undetectable group in the univariate (low: OR:1.40; 95%CI: 1.00-1.95; P = 0.050 and high: OR:1.50; 95%CI: 1.05-2.14; P = 0.027) and fully adjusted models (low: OR:1.41; 95%CI: 1.00-1.99; P = 0.048 and high: OR:1.48; 95%CI: 1.03-2.14; P = 0.035). For women, there was no statistically significant association between TPOAb categories and elevated hs-CRP levels (low: OR: 0.98; 95%CI: 0.73-1.32; P = 0.941; high: OR:1.19; 95%CI: 0.87-1.64; P = 0.278; positivity: OR:1.08; 95%CI: 0.78-1.50; P = 0.637). After excluding participants with clinical thyroid diseases, the results remained similar. However, for men, only the high detectable group showed statistically higher odds of having elevated hs-CRP (OR:1.46; 95%CI: 1.00-2.11; P = 0.048). The associations for low detectable and positive TPOAb were marginal (low: OR:1.40; 95%CI: 0.99-1.98; P = 0.058 and positive: OR:1.50; 95%CI: 0.98-2.31; P = 0.062).

Conclusion: We found an association between TPOAb and hs-CRP levels among men, which persisted even when thyroid function was considered. These findings corroborate previous literature showing the potential relevance of TPOAb detectability as an indicator of low-grade inflammation, particularly in the male population.