Thyroid dysfunction in elderly first-episode drug-naïve major depressive disorder patients with comorbid dyslipidemia: prevalence, clinical profile and associated factors

Background: Elderly major depressive disorder (MDD) patients often exhibit complex symptomatology and high rates of abnormal lipid metabolism (ALM), yet predictors of abnormal thyroid function in those with co-occurring lipid metabolism are not fully elucidated. This study aimed to investigate the relationship between thyroid function and ALM in first-episode, drug-naïve (FEDN) elderly MDD patients. Methods: 1,029 elderly FEDN MDD patients were enrolled. Demographics, lipid profile (TC, TG, LDL-C, HDL-C), thyroid parameters (TSH, FT3, FT4, TG-Ab, TPO-Ab), and symptom ratings (HAMD, HAMA, PANSS-positive) were assessed. Results: Prevalence of abnormal thyroid function was 69.0%. Compared with ALM patients without thyroid dysfunction, those affected had higher HAMD, HAMA, and PANSS-positive scores, more suicide attempts, severe anxiety, and psychotic symptoms (all P < 0.05). Logistic regression identified BMI (OR = 1.186), HAMD score (OR = 1.201), blood glucose (OR = 4.03), TC (OR = 1.683), and LDL-C (OR = 1.299) were independent associated factors for abnormal thyroid function in MDD patients with comorbid ALM(all P < 0.001). Conclusion: Abnormal thyroid function is highly prevalent in elderly FEDN MDD patients with ALM; clinical severity, glucose, and lipid levels contribute to this comorbidity. These findings suggest that elderly, first-episode MDD patients with dyslipidemia, particularly those with elevated BMI, high blood glucose, and severe depressive symptoms, should undergo routine screening for thyroid dysfunction to facilitate early intervention.