Effects of TSH, fT3 and fT4 levels on neurocognitive symptoms in patients with schizophrenia

Purpose: The aim of this study is to examine the relationship between thyroid hormone levels and positive, negative, general, and cognitive symptoms in euthyroid patients with psychosis. Materials and Methods: Thirty-three schizophrenia patients were included in this cross-sectional study. Sociodemographic and clinical data of the participants, positive and negative symptoms assessment scale (PANSS), general assessment of functionality scale (GAF), and clinical global impression scale (CGI) scores were recorded. The relationships between TSH, fT3, and fT4 levels and cognitive performances of patients which is measured via a neurocognitive battery consisting of Trail Making Test (TMT) A, TMT B, verbal fluency test (VFT), digit span (DS), forward and backward, and Wisconsin Card Sorting Test (WCST) were investigated. Results: Significant correlations were found between fT3 levels and WCST performances. fT3 levels was significantly correlated with the number of categories achieved in WCST (r=.508; p=0.003). A significant correlation was found between fT4 levels and TMT B (r=.376; p=0.031) and VFT (p=.355; p=0.043) performances. In the linear regression model, it was found that fT3 levels significantly predicted the number of categories achieved in WCST (UB=1.680; p=0.029). Conclusion: The results of our study suggested that fT3 has more significant effects, primarily on executive functions, compared to T4.