A perspective on the thyroid and depression.

There is extensive literature documenting an association between abnormalities of the hypothalamic-pituitary-thyroid axis and disorders of mood. However, the specific abnormality in thyroid functioning associated with primary affective disorder remains poorly understood. Various aspects of the relationship between thyroid functioning and affective illness are reviewed. Particular attention is paid to psychiatric symptoms and clinical thyroid disorders as well as abnormalities of basal thyroid hormone levels in depression and the use of thyroid hormones in the treatment of depressive illness. Current hypotheses regarding the association between altered thyroid functioning and depressive illness are critically reviewed.