The aims of this multicenter , 6-week , double-blind , randomized , placebo-controlled fixed-dose ( 300 g/d ) trial conducted from 2004 to 2009 were to assess efficacy and tolerability of levothyroxine adjunctive to continuing treatment with mood stabilizer and/or antidepressant medication for patients with bipolar I or II disorder , currently depressed ( DSM-IV ) , and to investigate gender differences in treatment response .