Article

Is Autoimmune Thyroiditis Part of the Genetic Vulnerability (or an Endophenotype) for Bipolar Disorder?

University of Groningen, Groningen, Groningen, Netherlands
Biological Psychiatry (Impact Factor: 10.26). 08/2007; 62(2):135-40. DOI: 10.1016/j.biopsych.2006.08.041
Source: PubMed

ABSTRACT

Both genetic and environmental factors are involved in the etiology of bipolar disorder; however, biological markers for the transmission of the bipolar genotype ("endophenotypes") have not been found. Autoimmune thyroiditis with raised levels of thyroperoxidase antibodies (TPO-Abs) is related to bipolar disorder and may be such an endophenotype. This study was intended to examine whether autoimmune thyroiditis is related to the disease itself, to the (genetic) vulnerability to develop bipolar disorder, or both.
Blood was collected from 22 monozygotic (MZ) and 29 dizygotic (DZ) bipolar twins and 35 healthy matched control twins to determine TPO-Abs.
The TPO-Abs were positive in 27% of the bipolar index twins, 29% of the monozygotic bipolar cotwins, 27% of the monozygotic nonbipolar cotwins, 25% of the dizygotic bipolar cotwins, 17% of the dizygotic nonbipolar cotwins, and in 16% of the control twins. Repeated measures analysis of covariance on log-transformed absolute TPO-Abs values revealed significantly increased mean TPO-Abs levels in discordant twin pairs as compared with healthy twin pairs, whereas no difference was found between bipolar patients and their (discordant) nonbipolar cotwins.
This study shows that autoimmune thyroiditis is related not only to bipolar disorder itself but also to the genetic vulnerability to develop the disorder. Autoimmune thyroiditis, with TPO-Abs as marker, is a possible endophenotype for bipolar disorder.

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    • "This theory is supported by findings of higher frequencies of comorbid autoimmune diseases, aberrant cytokine concentrations (e.g. tumor necrosis factor alpha, interleukin 4) and elevated inflammation-related gene expression in circulating monocytes and T cell activation (Drexhage et al., 2011; Munkholm et al., 2013; Padmos et al., 2008; Vonk et al., 2007). The corticolimbic theory is based on many studies demonstrating an overall hyperactivation of "
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    • "This finding was confirmed in a Dutch study (Oomen et al., 1996) particularly in patients with rapid cycling of bipolar disorders. Moreover a twin study indicated that AIT is associated with a genetic vulnerability to develop a bipolar disorder, i.e. it could be an endophenotype of the bipolar disorder (Vonk et al., 2007). Also it was shown that female offspring of bipolar parents have an increased risk to develop AIT (Hillegers et al., 2007). "
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    ABSTRACT: Hashimoto’s thyroiditis (HT) is the most frequent cause of hypothyroidism in areas with sufficient iodine intake. While the impact of thyroid function on mood and cognition is well known, only in the recent years, an increasing number of studies report on the association of HT with cognitive and affective disturbances also in the euthyroid state. Recent imaging studies have shown that these impairments are accompanied by altered brain perfusion, in particular, in the frontal lobe and a reduced grey matter density in the left inferior gyrus frontalis. Brain function abnormalities in euthyroid patients with HT may be subtle and only detected by specific testing or even severe as it is the case in the rare neuropsychiatric disorder Hashimoto’s encephalopathy (HE). The good response to glucocorticoids in patients with HE indicates an autoimmune origin. In line with this, the cognitive deficits and the high psycho-social burden in euthyroid HT patients without apparent signs of encephalopathy appear to be associated with anti-thyroid peroxidase auto-antibody (TPO Abs) levels. Though in-vitro studies showing binding of TPO Abs to human cerebellar astrocytes point to a potential direct role of TPO Abs in the pathogenesis of brain abnormalities in HT patients, TPO Abs may function only as a marker of an autoimmune disorder of the central nervous system. In line with this, anti-central nervous system auto-antibodies (CNS Abs) which are markedly increased in patients with HT disturb myelinogenesis in-vitro and, therefore, may impair myelin sheath integrity. In addition, in HT patients, production of monocyte- and T-lymphocyte-derived cytokines is also markedly increased which may negatively affect multiple neurotransmitters and, consequently, diverse brain neurocircuits.
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    • "There is a significant correlation between family history of mood disorder in first degree relatives and patients having hypothyroidism. This may suggest a possible genetic connection, perhaps an inherited vulnerability as indicated by a genetic study in the Chinese population.[17] In another study of the female offspring of bipolar parents, children of parents with bipolar disorder were found to be more vulnerable to develop thyroid autoimmunity, independently of their vulnerability to develop psychiatric disorders.[18] "
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