TG and bipolar disorder: Levothyroxine (T4) and Liothyronine (T3) are widely used as an add‐on treatment and proved to be effective in improving treatment response in euthyroid patients with refractory or bipolar depression (M. Bauer et al., 1998) or bipolar depression (M. Bauer et al., 2005) probably by modulating the brain serotonin system (Mason et al., 1987), which might partly explain the role of thyroid hormone in the pathophysiology of affective disorders.