Thyroid Disease and Mental Disorders: Cause and Effect or Only comorbidity?

Robertas Bunevičius; Arthur J. Prange Jr

Disclosures

Curr Opin Psychiatry. 2010;23(4):363-368. 

In This Article

Community Studies

Recent community-based studies reported that thyrotropin concentrations were positively associated with increased risk for depression in middle-aged women[10] and negatively associated with depressed mood in men.[11] It was also reported that, in euthyroid men, elevated T4 concentrations (within the normal range) increased the risk for chronic depression.[12] These findings contradict reports of community-based studies performed in the general adult population[13] and in an elderly population[14] that found no association between overt or subclinical thyroid dysfunction and mood symptoms. In fact, one study[13] reported that biochemical hypothyroidism was associated with decreased prevalence of depression and anxiety. However, recent further analyses of this large database,[15•] when treatment with T4 was taken into consideration, revealed significant differences in association between mood symptoms and thyroid functioning. In untreated patients, an inverse association between thyrotropin concentrations and scores of depression and anxiety was found. Contrariwise, in patients treated with T4, a positive association between thyrotropin concentrations and symptoms of depression and anxiety was found. These findings may have simple explanations. For example, patients with mood symptoms may take less thyroid medication. However, the findings may also have a physiological basis: treatment with T4 may affect natural regulation of thyroid axis functioning, resulting in presentation of mental symptoms. Meta-analyses of community-based studies[12] revealed that symptoms of depression are associated not only with increased T4 concentrations but also with decreased thyrotropin concentrations (indicating thyroid hyperactivity). The authors concluded that the effects of thyroid hormone on mood differ in normal populations compared with patients with thyroid disease.

Pregnancy causes profound endocrine changes, including changes in thyroid axis functioning. For example, during early pregnancy, elevated chorionic gonadotropin concentrations exert a significant thyroid gland-stimulating effect. A recent follow-up study[16] of a cohort of pregnant women confirmed a relationship between presence of depression and high free T4 concentrations with a strong trend toward lower thyrotropin concentrations and higher prevalence of subclinical hyperthyroidism during late pregnancy. These findings are relevant to earlier reports about an association between low thyrotropin concentrations and depression during pregnancy.[17] In contrast to gestational depression, early postnatal depression is associated with lower serum thyroid hormone concentrations in late pregnancy.[18,19]

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