Neutrophil-to-Lymphocyte Ratio, Platelet-to-Lymphocyte Ratio, and C-Reactive Protein as Risk Markers in Thyroid Autoimmunity, Hypothyroidism, and Hyperthyroidism: A Cross-Sectional Study

Autoimmune thyroid disease is common, and low-grade systemic inflammation has been proposed as a contributing mechanism. The neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and C-reactive protein (CRP) are inexpen-sive, widely available inflammatory markers whose value as risk indicators for thyroid autoimmunity and thyroid dysfunction remains incompletely defined. In the present study, we aimed to evaluate whether NLR, PLR, and CRP—alone, combined, and ad-justed for sociodemographic, clinical, habit-related, and laboratory covariates—are associated with thyroid autoimmunity and with alterations in thyroid status. A cross-sectional analysis was conduced in 3,406 adults; participants were measured with TSH, FT4, thyroid antibodies (TRAb, TPOAb, and TgAb), complete blood count, and high-sensitivity CRP values, inter alia. The prevalence of any thyroid status alter-ation was 52.2%, and of thyroid autoimmunity, 39.2%. In multivariable analysis, NLR and PLR were strongly and independently associated with thyroid autoimmunity (both p< 0.001); CRP showed a more modest association (p=0.033). NLR achieved an AUC of 0.752 for autoimmunity. None of the three markers discriminated thyroid status alter-ation overall, but CRP remained independently associated with it and showed a stronger effect within the antibody-positive subgroup. In conclusion, NLR and PLR are robust, independent correlates of thyroid autoimmunity but not of thyroid status al-teration per se, whereas CRP shows a modest but consistent association with both out-comes, particularly in antibody-positive patients. These low-cost markers may com-plement antibody testing for risk stratification in autoimmune thyroid disease.