TPO and major depressive disorder: (2019) indicated that compared to non‐suicide attempters, suicide attempters had higher serum levels of anti‐thyroglobulin (TgAb) and thyroid peroxidases antibody (TPOAb) in first‐episode and drug‐naïve patients with major depressive disorder, and thus they proposed that TgAb and TPOAb could become promising biomarkers for predicting suicide risk in major depressive disorder.