Source: Circulation  |  Posted 10 years ago

Patients with bipolar disorder are particularly sensitive to thyroid function variations, even within the normal range.

"Our results suggest that nearly three-quarters of patients with bipolar disorder have a thyroid profile that may be sub-optimal for antidepressant response," say United States researchers. "It remains to be seen whether pharmacological enhancement of thyroid function will facilitate recovery from bipolar depression."

Investigators point out that treatment of the depression phase of bipolar disorder is a clinical challenge. They also note that hypothyroidism is known to be associated with depression.

They studied 65 patients in the depressed phase of bipolar I disorder to test the hypothesis that patients with lower thyroid function, even within the normal range, might have a poorer response to treatment initially.

Researchers determined thyroid function in participants using a panel of thyroid measures. These included thyroid-stimulating hormone (TSH), thyroxine, triiodothyronine resin uptake and the free thyroxine index (FTI). They then initiated algorithm-guided treatment.

Investigators estimated the effect of each thyroid measurement on time to remission using the Cox proportional hazards model.

"Both lower values of FTI and higher values of TSH were significantly associated with longer times to remission," they report.

"Outcomes were relatively poor unless patients had FTI values above the median and TSH values below the median.

"Patients with this optimal profile experienced remission four months faster than the remainder of the study group."