[The relation between thyroid function and depression: a review].

OBJECTIVE The role of the thyroid gland in primary depressive disorder is unclear. Although there is evidence that patients with subtle underlying defects in thyroid function may be more prone to developing depressive disease, the specific abnormality in thyroid function associated with depressive disorders remains poorly understood. In this review, we outline the major findings concerning depression and thyroid function, with particular attention on the relationship between thyroid function and cerebral monoamines. METHODS Literature searches were performed by Medline, with secondary-source follow-up. RESULTS The documented hypothalamus-pituitary-thyroid (HPT) axis abnormalities in some depressed patients are: elevated T4 concentrations, abnormal TSH responses to TRH; presence of antithyroid antibodies and elevated CSF - TRH concentrations. The relation of these abnormalities of HPT function, the main monoamines and the diagnostic subtypes of patients with depression is complex and does not directly support a linear relationship. CONCLUSIONS After many years of research, the precise relationship between the HPT axis and depressive disorders remains obscure, and the mechanism underlying the thyroid abnormalities in depressive patients remains indeterminate. Thus, considerable further investigation will be necessary to understand the role of the HPT axis in the pathogenesis and treatment of depressive disorders.