Appearance of mania in drug-resistant bipolar depressed patients after treatment with L-triiodothyronine.

L-Triiodothyronine (T3) has been reported to potentiate the antidepressant effects of tricyclic antidepressants (TCAs) in patients who do not respond to these drugs, while thyroxine (T4) has been used to treat rapid-cycling bipolar disorder patients. The development of mania in antidepressant-resistant bipolar depressed patients after T3 was added to their antidepressant treatment is reported. It is speculated that thyroid hormone-catecholamine receptor interaction might underlie these T3-associated clinical manifestations. It is concluded that T3 did not prevent the switch to mania in the bipolar depressed patients reported here. Further study is necessary to determine if T3 plays a role in promoting the switch to mania in depressed patients treated with T3 in conjunction with TCAs, and if bipolar depressed patients are particularly vulnerable to mania from the combined effects of TCAs and T3.