Thyroglobulin antibodies and risk of readmission at one year in subjects with bipolar disorder

Thyroid autoimmunity has been proposed as an endophenotype for Bipolar Disorder (BD), although its relationship with clinical outcomes remains unclear. We aimed to determine whether thyroid autoimmune status (thyroperoxidase antibodies [TPO-Abs] and thyroglobulin antibodies [TG-Abs]) in BD is associated with a greater risk for readmission at one year. We studied 77 inpatients with BD admitted for an index manic or mixed episode. Serum thyroid antibodies (TPO-Abs and TG-Abs) were determined at admission. We compared the readmission risk at 1 year, based on patients׳ thyroid autoimmunity profile using survival analyses. Cox regression was used to control covariates. TG-Abs+ but not TPO-Abs+ was associated with a lower risk of relapse. The Kaplan–Meier mean estimated survival times were 341.6 days (CI95% 316.4–366.8) for the TG-Abs+ group and 261.9 days (CI95%: 221.8 to 302.0) for the TG-Abs− group. Cox proportional hazards regression indicated that subjects with TG-Abs+ were 3.7 (1/OR=1/0.27) times less likely to get admitted during the follow-up period than those with TG-Abs−. Our study suggests that an autoimmune biomarker in patients with BD (i.e., the presence of TG-Abs) is associated with a lower risk of psychiatric readmission after an index hospitalization for a manic or mixed episode.