Affective Disorders Associated With Autoimmune Thyroiditis

SIR: Mood disorders often are associated with thyroid dysregulations, particularly depressions with autoimmune thyroiditis.^1,2 In the general population, the prevalence rate of autoimmune thyroiditis (Hashimoto's disease) is about 5% to 12%^1,2 (depending on the criteria used for definition), and it manifests with characteristic, though unspecific, high titers of autoantibodies, but not always with clinical symptoms.^2,3 The goal of this study was to investigate thyroid diseases in psychotic patients in view of the prevalence of autoimmune thyroiditis in clinical practice.

In a retrospective study design, all files of inpatients with affective or schizoaffective disorders or schizophrenia (DSM-IV criteria) from the Department of Psychiatry and Psychology, University of Göttingen, Germany, were evaluated between January 1994 and May 2000. Blood thyroid hormones in vitro (T₃, T₄, TSH) were examined, autoantibodies to thyroid peroxidase (anti-TPO) were analyzed by a DYNO anti-TPO assay (BRAHMS Diagnostica, Berlin, Germany; cutoff for positivity >60 U/ml).

In all, out of 1,782 inpatients with acute psychosis, 109 patients (6.1%; 64 females, 45 males; mean age 48.4 years) had pathological thyroid findings. We found 20 patients (15 females, 5 males; mean age 61.9 years) with an autoimmune thyroiditis. Of these, 6 patients suffered from hypothyroidism, 2 patients from hyperthyroidism, and the other 12 had an euthyroid status. One patient met the criteria for a Hashimoto encephalopathy.⁴ Relevant factors for an autoimmune thyroiditis were gender and age of patients and type of psychiatric diagnosis (depressive disorder, n=11; bipolar disorder, n=5; schizoaffective disorder, n=3; schizophrenia, n=1).

We observed strong differences between different subtypes of depressive disorders in their association with autoimmune thyroiditis. Most patients with autoimmune thyroiditis were suffering from a unipolar recurrent major depression. There was no trend to a higher prevalence of autoimmune thyroiditis in affective disorders in comparison to the general population. The higher prevalence rates of Hashimoto's disease in women and in older patients were expected from the literature.⁵

Autoimmune thyroid dysfunctions warrant further testing in patients with acute mood disorders (e.g., additional sonography, needle biopsy) and probably offer new immunological considerations for psychopathology, etiology, and nosology of affective disorders and for treatment of risk groups (elderly women and nonresponders). Psychotic diseases and associated dysfunctions of the hypothalamus-pituitary-thyroid axis possibly are a complex interdependent system, and the coexistence of Hashimoto's thyroiditis and affective disorders may be an effect of common biological pathways.