The Influence of Thyroid Hormones on Brain Structure and Function in Humans

Area of Science:

• Neuroendocrinology
• Neurobiology
• Brain Imaging

Background:

• Thyroid hormones (TH) exert widespread effects through organ-specific mechanisms involving transporters, deiodinases, and receptors.
• Understanding TH's precise role in the brain is crucial due to its pleiotropic actions.

Purpose of the Study:

• To investigate the effects of experimentally induced thyroid hormone imbalances on brain structure and function in humans.
• To identify specific brain regions and networks sensitive to thyroid hormone levels.

Main Methods:

• Utilized a human volunteer model with experimentally induced mild hyperthyroidism and subclinical hypothyroidism.
• Employed comprehensive neuropsychological testing batteries.
• Integrated structural and functional multimodal neuroimaging techniques, including voxel-based morphometry and resting-state functional connectivity.

Main Results:

• Mild thyrotoxicosis induced significant changes in brain structure, resting-state functional connectivity, and working memory task-related activation.
• Subclinical hypothyroidism also resulted in detectable alterations in multiple functional and structural brain measures.
• The cerebellum was identified as a key brain region responsive to thyroid hormone levels.

Conclusions:

• Thyroid hormone levels critically influence brain structure and function, impacting cognitive processes like working memory.
• The cerebellum plays a significant role in mediating the central effects of thyroid hormones.
• These findings highlight the importance of maintaining euthyroidism for optimal brain health and cognitive performance.