Triiodothyronine addition to paroxetine in the treatment of major depressive disorder.

There is evidence that thyroid hormone T3 increases serotonergic neurotransmission. Therefore, T3 addition to antidepressants may improve treatment response in major depression. In nonrefractory depression, T3 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 T3 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 T3 (25 microg), high-dose T3 (25 microg 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 > or = 50%) was 46% in all three treatment arms (P = 0.99). T3 addition did not accelerate clinical response to paroxetine, nor was an effect of T3 found when only women were analyzed. Patients on T3 addition reported more adverse events than patients on placebo comedication. In conclusion, these results do not support a role for T3 addition to selective serotonin reuptake inhibitors in the treatment of nonrefractory major depressive disorder. On the contrary, more adverse reactions occurred in T3-treated patients.