THYROID-HORMONES, THE BRAIN, AND AFFECTIVE-DISORDERS

Clinical thyroid disorders are frequently associated with psychiatric symptomatology, thus supporting a role for thyroid hormones in the bio logical basis of psychiatric disorders, particularly mood disorders. D espite extensive literature documenting various abnormalities of thyro id function tests in primary major depression, the role of thyroid hor mones in the pathophysiology of affective disorders remains to be clar ified. In this review, we describe the various abnormalities of thyroi d hormone levels reported in primary affective illness. We also review the competing hypotheses to explain the abnormalities of thyroid func tion observed. Although neither model can fully explain the role of th yroid hormones in depressive illness, they provide working hypotheses for further study. Additional research is required to clarify the regu lation of thyroid hormones by mature brain and the role of these hormo nes in the biological basis of affective illness.