Unconventional uses of thyroid hormones: Psychiatric indications in mood disorder
P Whybrow, M Bauer & L Altshuler
Thyroid hormones have been employed for 3 decades as adjunct treatments in depression and the stabilization of manic depression, especially in women. After a brief historical review, two studies will be presented to highlight this 'drug' use of thyroid hormone.
(1) A meta analysis of six studies on the use of thyroid hormone to accelerate antidepressant response. Five studies found T3 to be significantly more effective than placebo, especially in women.
(2) An FDG-PET study demonstrating changes in regional brain metabolism with supra physiological doses of T4 in bipolar disorder. Ten depressed women with bipolar disorder receiving antidepressant and/or mood stabilizers participated in two FDG-PET scans, one prior to and another after a 7-week open-label trial of T4 administration. Relative glucose metabolism in individual brain regions was calculated from decay-corrected raw counts of radioactivity in 10 bilateral regions using a volume of interest (VOI) approach. In addition, a voxel-by-voxel method SPM99 was used. Of the 10 depressed women, 7 were full responders and 3 women were partial responders to treatment. VOI analysis indicated a relative increase in metabolism in the left middle frontal gyrus, a decrease in the left hippocampus and left amygdala. (SPM99) analysis also supported T4-induced deactivation of limbic structures indicating that T4 may improve mood by actions on the specific subcortical circuits that have been characterized as abnormal in affective illness by other investigators.