Peripheral thyroid hormone levels in treatment resistant depression

Background: Various abnormalities of thyroid function have been inconsistently reported in major depression. The inconsistency between studies may be due to several factors including the stage of treatment resistance. Methods: One hundred and one patients with major depressive disorder receiving their first antidepressant for their current major depressant episode had baseline thyroid function test performed. On completion of treatment, their stage of antidepressant resistance was determined. Results: Severity of depression but not any peripheral thyroid hormone level was associated with stage of antidepressant treatment resistance. Conclusions: Stage of treatment resistance does not appear to be a factor in the variability in peripheral thyroid hormone levels in unipolar major depression.