TPO and major depressive disorder: Among the 266 older MDD patients, compared to older MDD patients without SCH, patients with SCH have a longer disease progression (P < 0.001), longer married (P = 0.007), higher HAMD values (P < 0.001), higher positive total score values (P = 0.002), higher CGI (P = 0.004), higher BMI (P = 0.008), higher attempted suicide (P = 0.017), and higher levels of TSH (P < 0.001), A-TG (P = 0.002), A-TPO (P < 0.001), HDL-C (P < 0.001), LDL-C (P < 0.001), TC (P < 0.001), FPG (P < 0.001), systolic pressure (P < 0.001).