TG and hypothyroidism: With the identification of triiodothyronine (LT3) and levothyroxine (LT4) as the principal thyroid hormones in the 1950s [8], the effect of these hormones, alone and in combination (adjunctive) with standard psychotropic medications, has been studied repeatedly in the treatment of patients with affective disorders, including those without metabolic evidence of peripheral thyroid dysfunction, e.g., hypothyroidism [9].