Triiodothyronine (T3) supplementation in major depressive disorder

Introduction The use of thyroid hormones to enhance the effects of antidepressants is based on evidence supporting a link between thyroid function and Major Depressive Disorder. Thyroid abnormalities have been found in patients with Major Depressive Disorder and have been correlated with depression severity. Symptoms associated with clinical hypothyroidism include mood disturbances, primarily depression. In addition, an increase in antidepressant treatment resistance has been associated with thyroid abnormalities. This article reviews the existing data regarding triiodothyronine (T3) supplementation of antidepressants in the treatment of major depressive disorder. Methods Medline and EMBASE were searched from 1996 to November 2014 using the key terms triiodothyronine, T3, and treatment-resistant depression. Results T3 may increase serotonergic neurotransmission and has been studied as an add-on agent in patients with unipolar depression with and without thyroid dysfunction to accelerate, enhance, and augment the effects of tricyclic antidepressants and selective serotonin reuptake inhibitors. Discussion Data support the use of T3 augmentation (25-50 μg/d) for the treatment of depressive symptoms in some patient populations without thyroid hormone abnormalities who do not respond to an adequate trial of a tricyclic antidepressant or a selective serotonin reuptake inhibitor. Monitoring for adverse effects and conditions that may be exacerbated by T3 augmentation is recommended.