Comparison of Thyroid Hormone Levels Between Patients With Major Depressive Disorder and Healthy Individuals in China

Abnormal thyroid function in major depressive disorder (MDD) has been studied extensively, but the results still remain inconsistent. In China, few large-scale studies have investigated the differences in the levels of thyroid hormones between patients with MDD and healthy controls (HCs). In this retrospective, cross-sectional study, 535 MDD patients and 998 HCs were included. We compared the levels of thyroid hormones (FT3, FT4, and TSH) between the two groups, as well as investigated the distribution of levels of thyroid hormones within and outside normal ranges. The results showed that all the three hormones were significantly lower in MDD patients than in HCs, which was also true in different gender and age subgroups. The proportion of subjects with levels of all the three hormones outside the normal range in the MDD group was higher than that in the HC group (all p < 0.05). However, no significant difference was found in clinical/subclinical hyperthyroidism or hypothyroidism between the two groups (p > 0.05). Our study showed that the levels of thyroid hormones were lower in MDD patients, suggesting that there was an association between abnormal thyroid function and depression. The higher rate of thyroid dysfunction in MDD patients indicated the importance of regular monitoring of thyroid function.

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 T(4) 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 FT(4) index (FT(4)I) and HLOS was present in men, but not in women. The mean HLOS stratified by gender and median FT(4)I was 50% shorter in men with a relatively high FT(4)I 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 FT(4) 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.