Differences in thyroid function between bipolar manic and mixed states

Background: High rates of thyroid axis abnormalities have been reported in most studies of patients with rapid-cyclin bipolar disorder. Mixed states share similarities with rapid-cycling, including close temporal occurrence of manic and depressive symptoms, predominance in women, poor outcome, and less robust response to lithium compared with pure mania; however, thyroid axis abnormalities have not been well studied in mixed mania. Methods: To test the hypothesis that mixed states are associated with a higher prevalence of hypothyroidism than pure mania, immunoreactive triiodothyronine (T-3), thyroxine (T-4), and thyroid-stimulating hormone (TSH) concentrations were determined from serum obtained at the time of admission in 37 consecutive patients with DSM-III-R bipolar disorder, manic or mixed. Results: The mean TSH concentration was significantly higher, and the mean T-4 concentration was significantly lower in patients with mixed mania compared with pure mania. There were no significant differences in T-3 concentration or in previous lithium exposure. Conclusions: These findings suggest thyroid axis dysfunction is more common in bipolar mixed than in bipolar manic patients. (C) 1998 Society of Biological Psychiatry.