Background: Thyroid hormone plays a role in both serotonin and catecholamine functions in the brain, and has been linked to abnormal mood states in bipolar disorder. Unlike most studies which have included only patients with bipolar I, this study evaluated triiodothyronine (T3) as an augmentation agent for treatment-resistant depression in patients with bipolar II and bipolar disorder NOS.

Methods: This study was a retrospective chart review of patients treated in a private clinic between 2002 and 2006. The charts of 125 patients with bipolar II disorder and 34 patients with bipolar disorder NOS were reviewed.

Results: Patients had been unsuccessfully treated with an average of 14 other medications before starting T3. At an average dose of 90.4 mcg (range 13 mcg-188 mcg) the medication was well tolerated. None of the patients experienced a switch into hypomania, and only 16 discontinued due to side effects. Improvement was experienced by 84%, and 33% experienced full remission.

Limitations: The limitations are those associated with the retrospective chart review design.

Conclusions: A high percentage of bipolar II and bipolar NOS patients with treatment resistant depression improved on T3. Despite the use of higher than usual doses in many of the patients, the medication was well tolerated. Augmentation with supraphysiologic doses of T3 should be considered in cases of treatment resistant bipolar depression.