Retrospective analysis of thyroid function in drug-free patients with bipolar disorder in China

Background: Bipolar disorder is a common mental illness with serious consequences. Clinical studies have found that thyroid function may have an impact on patients with bipolar disorder, but there are few relevant studies in China. So this study explores the characteristics of thyroid function in patients with bipolar disorder in China.Methods Using retrospective cohort study and a cross-sectional study, thyroid function tests were performed in inpatients from September 2015 to January 2018 in the Second Affiliated Hospital of Xinxiang Medical University, who were diagnosed with bipolar disorder and were not treated with medications for at least three months before hospitalization.Results We found that the triiodothyronine (T3) and free triiodothyronine (FT3) levels were significantly higher in bipolar mania than in bipolar depression (P < 0.01). The thyroid stimulating hormone (TSH) levels were significantly lower in male than female patients, while the FT3, free thyroxine (FT4) levels were higher in male than female patients (P < 0.01). Patients were divided into two groups: those who used lithium and those who did not. Both groups had a tendency of hypothyroidism after treatment. In addition, the T3 and FT3 levels were significantly higher in manic than in depressive status in those patients who had a transition between mania and depression in 28 patients compared with previous hospitalization (P < 0.05).Conclusion Patients with bipolar disorder may develop thyroid dysfunction at different stages and in male/female sexes.