[Depressions resistant to tricyclic antidepressive treatment and hypothyroidism]

The relationship between thyroid disorders and depression is well known. This type of endocrine disease is mainly observed in patients with depression resistant to appropriate antidepressor therapy. Three clinical forms of this association may be distinguished: hypothyroidism in a patient with depression but without a previous psychiatric history; a relapse of depression in a manico depressive patient who has developed hypothyroidism; the finding of slight thyroid dysfunction (increased TSH response after injection of TRH) in a patient with depression. The frequency of the association of hypothyroidism and resistant depression underlines the need to perform thyroid function tests in all depressed patients who do not respond normally to appropriate antidepressor therapy. The precise mechanism of the resistance of depressive symptoms to tricyclic antidepressors is unclear. Several arguments point to an effect of triiodothyronine on central noradrenergic receptors. In practice, significant hypothyroidism implies substitute therapy. Minor thyroid dysfunction (abnormal TRH test alone) may require the association of tricyclic antidepressors and thyroid hormone although the indications and precise dosages of this drug association have not been established.