Low triiodothyronine (T3) levels predict worse outcomes in autoimmune encephalitis—A meta‐analysis of current literature

Abstract

Abstract Introduction An unusual association between thyroid dysfunction and autoimmune encephalitis (AE) was noticed when patients presented with low free triiodothyronine (fT3) levels and antithyroid antibodies. We conducted a meta‐analysis to investigate whether thyroid dysfunction, that is, lower fT3 levels are associated with worsening clinical manifestations and prognosis in patients with AE. Methods Literature search of five electronic databases was performed till April 5, 2023. Inclusion criteria were as follows: Observational studies reporting patients with all subtypes of AE and assessing thyroid dysfunction categorized as low fT3 and non‐low fT3. Primary endpoints included modified Rankin scale (mRS) at admission, abnormal magnetic resonance imaging, length of stay, seizures, and consciousness declination. Results Comprehensive literature search resulted in 5127 studies. After duplicate removal and full‐text screening, six observational studies were included in this analysis. Patients with low fT3 were 2.95 times more likely to experience consciousness declination (p = .0003), had higher mRS at admission (p < .00001), had 3.14 times increased chances of having a tumor (p = .003), were 3.88 times more likely to experience central hypoventilation, and were 2.36 times more likely to have positivity for antithyroid antibodies (p = .009) as compared to patients with non‐low fT3. Conclusion The findings of our study suggest that low fT3 levels might be related to a more severe disease state, implying the significance of thyroid hormones in AE pathogenesis. This finding is crucial in not only improving the early diagnosis of severe AE but also in the efficient management of the disease.

Keywords

• antibody
• antithyroid
• autoimmune
• encephalitis
• meta‐analysis