Neuropsychiatric manifestations of thyroid disease.

The interface between thyroid hormone action and neuropsychiatric function is intricate, and several mechanisms of thyroid hormone uptake into brain tissues, hormone activation, and influences on neurotransmitter generation have been identified. Symptoms of hypothyroidism are nonspecific, whereas those attributed to thyrotoxicosis may be more characteristic. Neuropsychiatric manifestations triggered by thyroid dysfunction likely respond well to reestablishment of the euthyroid state, although some patients have persistent complaints. The addition of LT3 to ongoing LT4 replacement has yet to be definitively shown to be advantageous. Treatment of euthyroid depression with LT3 in addition to antidepressant therapy lacks convincing evidence of superior outcomes.