Deiodinase variation and liothyronine treatment interaction to accelerate ECT response in major depression: Pilot data and implications for thyroid pharmacogenomic testing in mood disorders

Background: Concurrent liothyronine treatment has been shown to accelerate time to response in patients treated for major depression. However, the relationship between genetic variation in deiodinase and T3 treatment response has received little investigation. Methods: This is a post-hoc analysis of a randomized, double-blind, placebo-controlled trial of concurrent liothyronine (T3-Cytomel®, n = 23; mean dose 46.3 ± 3.3 mcg) in patients with major depression where a clinical recommendation was made to pursue ECT. The primary outcome measure was time to 50% reduction in depressive symptoms. Multivariable linear models were used to examine effect of T3 and placebo and genetic variants as predictors of change in HAMD24 and number of ECT treatments. Results: Survival analysis did not show a significant effect for the T3 + ECT group achieving a faster time to response compared to placebo + ECT (p + ECT). Survival analysis for RUL lead placement alone showed a significant effect for the T3 + ECT group achieving a faster time to response compared to p + ECT (p = 0.01) with significantly fewer ECT treatments (p = 0.03). Carriers of the functional SNP rs11206244 gene DI01-C785T minor allele (TT and CT) vs. non-carriers (CC), showed fewer ECT treatments in the T3 + ECT group, compared to p + ECT (5.3 ± 1.0 vs. 8.3 ± 2.1, p = 0.045). Conclusions: These pilot data identify clinically relevant genetic variation in DI01- C785T contributing to an accelerated response time, but not an overall greater symptom reduction. Exogenous T3 supplementation may be therapeutic by attenuating a baseline DI01 relative functional deficit which functionally reduces peripheral conversion of T4 to biologically active T3. Further work is encouraged to assess genetic variation of thyroid deiodinase enzymes in larger samples of depressed patients to better optimize accelerating strategies to ECT and more broadly, thyroid augmentation strategies in major depressive and bipolar disorders.