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fMRI revealed neural substrate for reversible working memory dysfunction in subclinical hypothyroidism
De-Fa Zhu1, Zhao-Xin Wang, Da-Ren Zhang
1Department of Endocrinology, Anhui Geriatric Institute, The First Affiliated Hospital of Anhui Medical University Hefei, Anhui, China.
Brain : a Journal of Neurology
|August 22, 2006
Summary
Subclinical hypothyroidism (SCH) impairs working memory and frontoparietal brain networks. L-thyroxine treatment improved both memory performance and executive functions in SCH patients.
Area of Science:
- Neuroscience
- Endocrinology
- Cognitive Science
Background:
- Thyroid hormone imbalances, including hyperthyroidism and hypothyroidism, are known to affect cognitive function.
- The impact of subclinical hypothyroidism (SCH) on brain function and the necessity of hormone replacement therapy remain debated.
- Working memory and executive functions are critical cognitive domains potentially affected by thyroid status.
Purpose of the Study:
- To investigate the effects of subclinical hypothyroidism on working memory using functional MRI (fMRI).
- To examine the functional changes in the frontoparietal network during a working memory task in SCH patients.
- To assess the impact of l-thyroxine treatment on cognitive performance and brain function in SCH patients.
Main Methods:
- Functional MRI (fMRI) was employed to measure brain activity during a digit n-back working memory task.
- Participants included euthyroid subjects, hyperthyroid patients, and SCH patients (before and after treatment).
- Analysis focused on the load effect of blood oxygen level-dependent (BOLD) responses within key frontoparietal regions of interest (ROIs).
Main Results:
- SCH patients and hypothyroid patients performed significantly worse on the 2-back task compared to euthyroid and hyperthyroid subjects.
- In pre-treatment SCH patients, the working memory task load effect was diminished in frontal cortex ROIs but present in parietal and premotor areas.
- Following approximately 6 months of l-thyroxine (LT4) treatment, SCH patients showed normalized load effects in all frontal ROIs and improved task performance.
Conclusions:
- Subclinical hypothyroidism is associated with impaired working memory, specifically affecting the frontoparietal network.
- L-thyroxine replacement therapy can restore normal brain function in the frontoparietal network and improve working memory and executive functions in SCH patients.
- These findings suggest that hormone-replacement treatment may be beneficial for SCH patients experiencing cognitive deficits.