Oxcarbazepine was associated with risks of newly developed hypothyroxinaemia and impaired central set point of thyroid homeostasis in schizophrenia patients

Aim Hypothyroxinemia might be easily ignored, due to attention is typically paid to individuals with elevated thyroid stimulating hormone (TSH). In this study, we aimed to evaluate the association of oxcarbazepine use as adjuvant for treatment of schizophrenia with hypothyroxinemia and central set point of thyroid homeostasis. Methods This retrospective cohort study was conducted in the "Second Affiliated Hospital of Xinxiang Medical University". Inpatients with a diagnosis of schizophrenia admitted between January 2016 and October 2019 with normal thyroid function at admission were included. Oxcarbazepine use was the exposure measure. Newly developed hypothyroxinemia was the primary outcome measure and parameters of thyroid homeostasis central set point as measured by "TSH index" and "thyroid feedback quantile-based index (TFQI)" were the secondary outcome measures. Results A total of 1,207 eligible patients were included. The occurrence of hypothyroxinemia in patients who received oxcarbazepine was higher (35/107, 32.7%) than in those patients who did not (152/1099, 13.8%), with adjusted relative risk of 2.24 and 95% confidence interval of 1.57 and 3.17. Oxcarbazepine use was associated with greater reduction in TSH index (adjusted β -0.33 and 95% confidence interval -0.48, -0.19) and TFQI (adjusted β -0.24 and 95% confidence interval -0.31, -0.16). Conclusion Oxcarbazepine use was independently associated with increased risk of developing hypothyroxinemia, and greater reduction in TSH index and TFQI, suggesting that impaired central set point of thyroid homeostasis might be involved in the mechanism of oxcarbazepine induced hypothyroxinemia.