Thyroid Gland Volume Is Significantly Smaller in Patients With Psychiatric Disorders Than in Those Without Psychiatric Disorders

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To the Editor: The thyroid gland normally secretes thyroxine and triiodothyronine. A previous study reported that partial substitution of triiodothyronine for thyroxine improved mood and neuropsychological functions in hypothyroid patients treated with only thyroxine, suggesting an importance of the integrity of the thyroid gland for neuropsychological functions. It is clear that thyroid hormone plays an important role in the brain, influencing mood and cognition; however, the detail mechanisms remain to be elucidated.