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

Hyperthyroidism

In contrast to community samples, the vast majority of patients with overt hyperthyroidism will display a psychiatric disorder such as anxiety, mania, or depression. Severe hyperthyroidism may display delirium. Some patients may not meet the full criteria of a specific mental disorder, but they will not be free of mental symptoms such as tension, hyperactivity, or autonomic symptoms. The symptoms and signs of hyperthyroidism resemble those of primary mental disorders. Overactivity of the adrenergic system caused by hyperthyroidism may explain the similarity between the clinical presentations of hyperthyroidism and mania or anxiety, as well as the precipitating role of hyperthyroidism in the development of mania or anxiety disorder. It may also explain the increased sense of well being often experienced in the early stages of hyperthyroidism.^[20,21]

The relationship between hyperthyroidism and depression is less clear. Depression is usually linked to hypothyroidism, not to hyperthyroidism. However, prolonged hyperthyroidism might exhaust noradrenergic transmission and thus contribute to depression. Noradrenergic exhaustion might well occur in patients with hyperthyroidism who have bipolar disorder. In the initial phase of hyperthyroidism, thyroid hormone stimulation of the noradrenergic system may cause mania; later, when noradrenergic neurotransmission is exhausted, it may contribute to depression.^[21]

Mental symptoms and disorders secondary to hyperthyroidism should be treated first by restoring euthyroidism. Most mental symptoms, including depression, usually resolve once euthyroidism has been regained. Treatment with beta-adrenergic antagonists alone may quickly relieve many symptoms, including mental symptoms, even if euthyroidism is not restored,^[22] providing evidence that overactivity of the adrenergic system is largely responsible for mental symptoms in hyperthyroidism.

Cite this: Thyroid Disease and Mental Disorders: Cause and Effect or Only comorbidity? - Medscape - Jul 01, 2010.

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