Triiodothyronine addition to paroxetine in the treatment of major depressive disorder

There is evidence that thyroid hormone T-3 increases serotonergic neurotransmission. Therefore, T-3 addition to antidepressants may improve treatment response in major depression. In nonrefractory depression, T-3 addition to tricyclic antidepressants indeed accelerates treatment response. Current therapeutic practice favors selective serotonin reuptake inhibitors. This is the first study to investigate the efficacy of T-3 addition to paroxetine in major depression. One hundred thirteen patients with major depressive disorder were randomly assigned to 8 wk of double-blind outpatient treatment with low-dose T-3 (25 mug), high-dose T-3 (25 mug twice daily), or placebo in addition to paroxetine 30 mg daily. A total of 106 patients started treatment and were included in the outcome analysis. Response rate after 8 wk ( reduction of Hamilton Rating Scale for Depression score greater than or equal to 50%) was 46% in all three treatment arms (P = 0.99). T-3 addition did not accelerate clinical response to paroxetine, nor was an effect of T-3 found when only women were analyzed. Patients on T-3 addition reported more adverse events than patients on placebo comedication. In conclusion, these results do not support a role for T-3 addition to selective serotonin reuptake inhibitors in the treatment of nonrefractory major depressive disorder. On the contrary, more adverse reactions occurred in T-3-treated patients.