The Challenges and Complexities of Thyroid Hormone Replacement

Shayri M. Kansagra, BS; Christopher R. McCudden, PhD; Monte S. Willis, MD, PhD


Lab Med. 2010;41(6):229-348. 

In This Article

T3 Treatment Augments Psychiatric Therapy

Consistent with the animal models supporting specific needs for thyroid hormone in the brain are human studies demonstrating that T3 influences the potency of serotonin and catecholamine.[75–77] In a recent investigation of the role of T3 in treatment-resistant depression in patients with bipolar II disorder and bipolar disorder not otherwise specified (BP-NOS), 84% of the patients reported improved function, and 33% reported full remission.[78] Triiodothyronine has also been used to augment anti-depressants such as serotonin-specific reuptake inhibitors (SSRI)[79,80,81] and tricyclic antidepressants (TCAs).[82 83] Triiodothyronine augmentation for treating nonpsychotic major depressive disorder (MDD) with lithium has also been studied. While T3 augmentation did not improve symptoms, it was associated with fewer side effects and less attrition.[84] These studies have shown that T3 augmentation is promising for a number of psychiatric therapeutic regimens,[85] but its application in other diseases remains to be explored. It is possible that the improvements seen in T3/T4 combination therapy may reflect the effects of T3 on serotonin and catecholamine function in the brain.