Abstract
The present study was aimed to investigate the relationships between serum thyroid hormones (THs), frontal gray matter volume, and executive function in selected patients with major depressive disorder (MDD). One hundred and four MDD patients and seventy-five healthy controls (HCs) were subjected to thyroid-stimulating hormone (TSH), free Triiodothyronine (fT3), free Thyroxine (fT4), and executive function tests and underwent structural magnetic resonance imaging (MRI). Voxel-based morphometry (VBM) analysis was performed to compare group differences in the gray matter for the frontal lobe. Furthermore, mediation analysis was used to investigate whether gray matter volumes of the frontal gyrus mediated the relationship between serum THs and executive function in MDD patients. MDD patients exhibited significant gray matter volume reduction in several brain regions, including the left rectus, right middle frontal cortex, and left middle frontal cortex. Serum TSH levels are positively associated with altered regional gray matter volume patterns within MFG and executive function. Importantly, gray matter in the right MFG was a significant mediator between serum TSH levels and executive function. These findings expand our understanding of how thyroid function affects brain structure changes and executive function in MDD patients.
Highlights
Major depressive disorder (MDD) is a common and debilitating illness that affects millions of people worldwide
These findings suggest that the low serum thyroid-stimulating hormone (TSH) levels in MDD patients may be related to poor executive function performance, and the decreased gray matter may drive the TSHrelated executive impairment in the right middle frontal gyrus (MFG)
Consistent with previous studies, completed categories were lower, and total and perseveration errors were higher than in a healthy population [43]. These results indicate that MDD patients may exhibit different executive function deficits and have more difficulty adapting their behavior after negative feedback [44]
Summary
Major depressive disorder (MDD) is a common and debilitating illness that affects millions of people worldwide. Cognitive impairment often persists after remission of depressive symptoms in 30-50% of patients with MDD [5]. A recent study indicated that executive function might be the significant deficit in MDD and likely originated from disease duration’s cumulate effect [6]. Several studies have suggested that the changes in executive function in long-lasting depression showed a state-like phenomenon and were found to be improved by antidepressants and depression recovery [8, 9]. The currently available antidepressant drugs and behavioral therapies are not always effective in some patients. Many studies have demonstrated that changes in the neuroendocrine system could impair synaptic plasticity, leading to abnormalities in regional brain activity, including depressed mood and executive function [10]
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