Free T₄ index and clinical outcome in patients with depression

Introduction: Many studies of patients with major depression have reported that a significant decrease in serum free T₄ index is associated with specific treatments; what has been unanswered is whether these observations are generalizable. This study evaluated baseline thyroid function and its relationship to rapidity of treatment response as measured by hospital length of stay (HLOS). Methods: Admission thyroid indices and HLOS data were harvested from the medical record of patients hospitalized for depression, both unipolar and bipolar. The relationship between admission thyroid indices and HLOS was evaluated using survival models. Results: Controlling for age and year of discharge, an inverse relationship between FT₄ index (FT₄I) and HLOS was present in men, but not in women. The mean HLOS stratified by gender and median FT₄I was 50% shorter in men with a relatively high FT₄I in comparison to the other three groups. Limitations: This is a retrospective study limited by the absence of a structured diagnostic psychiatric interview and prospective controlled antidepressant evaluation. Conclusion: These data would suggest that a relatively elevated FT₄ index in depressed men is associated with a faster antidepressant response time. Prospective study is encouraged to further clarify this potential thyroid/gender relationship and whether thyroid supplementation can accelerate the improvement in depression as measured by HLOS.