Age-Related Differences in Depression Among Patients with Hypothyroidism: Associations of Irisin, Inflammatory Cytokines, and Immune Cell Ratios

Abstract

Objective: To evaluate age-related differences in depressive symptoms among patients with hypothyroidism and to assess their association with circulating irisin, inflammatory markers, immune cell ratios, and thyroid autoantibodies.Material and Methods: This cross-sectional study included 100 patients with hypothyroidism, stratified into two age groups (25–45 years and 45–65 years). Depressive symptoms were assessed using the Patient Health Questionnaire-9 (PHQ-9). Serum irisin and interleukin-6 levels were measured using enzyme-linked immunosorbent assay. Systemic inflammation was evaluated using neutrophil–lymphocyte ratio, monocyte–lymphocyte ratio, platelet count, and thyroid autoantibodies. Group comparisons, correlation analyses, and multivariate regression analysis were performed.Results: Patients aged 45–65 years showed significantly higher depression scores, increased interleukin-6 levels, neutrophil–lymphocyte ratio, monocyte–lymphocyte ratio, platelet counts, and thyroid autoantibody levels, along with significantly lower circulating irisin concentrations compared with younger patients. Irisin demonstrated a significant inverse association with depression severity, whereas inflammatory markers showed positive associations. Irisin and interleukin-6 remained independent predictors of depressive symptoms on multivariate analysis (p-value<0.05).Conclusion: Age-related immune–metabolic alterations are significantly associated with depressive symptoms in patients with hypothyroidism. Combined assessment of irisin and simple inflammatory markers may help identify individuals at higher risk of depression, particularly in older populations.