For patients with TSH ≤ 10.0 mIU/L, the introduction of levothyroxine therapy is individualized, depending on additional factors such as age, pregnancy planning and pregnancy, goiter, positive anti–thyroid peroxidase (anti-TPO) status, and presence of symptoms (fatigue, feelings of cold or dry skin, depression, heart function disorder, menstrual cycle disorder, etc.)(14). This evidence concerns the gene TPO and major depressive disorder.