Hashimoto’s encephalopathy: How a thyroid disease can cause psychosis

Psychosis has many causes, and more than 50 different medical conditions are known to cause psychosis. In many cases, psychosis might be the first sign of a medical illness or its most prominent symptom. Sometimes psychosis is the only noticeable symptom. In this article, I’ll discuss one of the many medical illnesses that can cause psychosis — Hashimoto’s encephalopathy.

Hashimoto’s thyroiditis vs. Hashimoto’s encephalopathy

What is Hashimoto’s Thyroiditis?

Hashimoto’s thyroiditis (also simply known as Hashimoto’s disease) is an autoimmune disease that affects the thyroid, a small gland in the neck that produces hormones and influences a variety of body functions. In Hashimoto’s thyroiditis, the immune system attacks the thyroid, causing inflammation and disrupting the production of thyroid hormones. This often leads to hypothyroidism (low levels of thyroid hormone) and can eventually cause physical symptoms such as fatigue, weight gain, and joint pain. Psychiatric symptoms such as depression and memory problems are also possible.

What is encephalopathy?

Encephalopathy is a broad medical term that generally means “brain disorder.” The literal translation from Greek is “brain suffering.” Encephalopathy is defined by global changes in cognitive or motor functioning. Symptoms of encephalopathy might include delusion, altered consciousness, mood changes, and changes in speech quality, just to name a few. Please note, it is important not to confuse encephalopathy with encephalitis — a word meaning “brain inflammation.” While these words are similar and easily confused, they describe different conditions.

What is Hashimoto’s encephalopathy?

Hashimoto’s encephalopathy is a rare disorder characterized by impaired brain function or altered mental status that is associated with the body making antibodies against its own thyroid gland. The disorder is also known as steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT). It’s also called Neurologic Disorder Associated with Thyroid Autoimmunity. These alternate names give a better picture of the processes behind the symptoms. 

What are the symptoms of Hashimoto’s encephalopathy?

Hashimoto’s encephalopathy was first described in 1966 by the aptly named Dr. Russel Brain. Dr. Brain coined the term while studying a 48-year-old man who had Hashimoto’s thyroiditis and experienced recurrent episodes of neurological and psychiatric symptoms that occurred during periods of normal thyroid function.

Typically, Hashimoto’s encephalopathy presents a combination of psychiatric and neurological changes, but many people have primarily psychiatric symptoms (Arrojo et al., 2007, Guirgis et al., 2014, Sporis et al., 2007, Matozzi et al., 2020). Most people also experience some neurological symptoms, possibly including muscle jerks, seizures, cognitive impairment, altered levels of consciousness, and more.

Interestingly, it is important to note that people with Hashimoto’s encephalopathy can often have normal thyroid-stimulating hormone (TSH) levels and may not have the typical clinical signs of hypothyroidism.

How is Hashimoto’s encephalopathy diagnosed?

Screening for antibodies against thyroid peroxidase, also known as anti-TPO antibodies, is the best marker for diagnosis as they are present in 95 to 100 percent of cases. However, 2 to 20 percent of the general, seemingly healthy population have anti-TPO present and can provide a false positive when tested. Therefore, diagnosing Hashimoto’s encephalopathy requires both a positive antibody test and clinical symptoms.

Another possible antibody marker to test for is anti-TG, or antibodies against thyroglobulin, a protein made by the thyroid that stores thyroid hormone. However, anti-TG screening can be a less reliable marker for Hashimoto’s encephalopathy than anti-TPO screening.

Brain wave studies (electroencephalograms, EEGs) can help confirm a diagnosis. EEG changes are present in 90 percent of Hashimoto’s encephalopathy cases.

How does Hashimoto’s encephalopathy cause psychosis?

There may be several processes by which the changes associated with Hashimoto’s encephalopathy lead to psychosis:

  • The antibodies that the body makes against the thyroid gland might also react against nerve cells, triggering an immune response in the brain.
  • The antibodies may also inflame the brain’s blood vessels, disrupting the flow of blood and oxygen to the brain.
  • Long-term hormone disruptions from the disease can lead to secondary effects on brain functioning.

How common is Hashimoto’s encephalopathy?

Hashimoto’s encephalopathy isn’t common. Just 2 cases per 100,000 people per year are documented, and only 400 cases have been reported in medical journals.

On the other hand, there is a pretty high rate of thyroid problems — including altered thyroid hormone levels and antibodies against the thyroid gland — among people with schizophrenia (Othman et al., 1994, Poyraz et al., 2008, Radhakrishnan et al., 2013). These findings illustrate the possible links between thyroiditis and psychosis. They also suggest that Hashimoto’s encephalopathy may be more common among people with schizophrenia or other mental illnesses.

Hashimoto’s encephalopathy treatment

There are three main courses of treatment for Hashimoto’s encephalopathy:

  • Immunomodulatory treatment, including therapeutic steroids, immunosuppression, intravenous immunoglobulins, and plasmapheresis
  • Thyroid hormone replacement
  • Antipsychotic medications

Should we routinely test for thyroid antibodies in people experiencing psychosis?

Most guidelines recommend testing for thyroid hormone levels as part of the medical evaluation for anyone with a first episode of psychosis. They probably should also recommend testing for the anti-TPO antibody.

We can’t assume that normal results on the standard thyroid tests of thyroid hormone levels will rule out Hashimoto’s encephalopathy. Thyroid hormone levels can be normal in many cases of Hashimoto’s encephalopathy, and up to 60% of people with Hashimoto’s encephalopathy won’t have had any thyroid issues prior to their first symptoms. Testing for anti-TPO antibodies costs less than $100 — and although it may result in some false positives and require thorough critical thinking to interpret the results — it may be a worthwhile addition to testing guidelines since approximately 30 percent of Hashimoto’s encephalopathy cases present with psychiatric symptoms.

Hashimoto’s encephalopathy can result in severe and permanent brain damage if it’s not treated in time, which provides further reason to add anti-TPO antibody screening to routine screening guidelines. If we detect it early, we can treat it effectively, and patients can go on with their lives. Since psychosis can be the first sign of Hashimoto’s encephalopathy, it makes sense that we should screen for it so that people can receive the right diagnosis and the right treatment as quickly as possible.

Finally, thyroid immunoreactivity was found to be associated with increased suicide risk in studies of major depression (Shen et al., 2019) and more severe psychosis symptoms in studies of schizophrenia (Barbero et al., 2020), so thyroid antibody levels could be an important a clinical marker for these other psychiatric outcomes.

Learn more:

You can find a lecture with more information on Hashimoto’s encephalopathy on my YouTube channel, 15-Minute Pharmacology. The lecture was given at the September 29, 2020 meeting of the SZconsult learning community.

Disclaimers

This article summarizes the results and conclusions of articles published in the medical literature. It is for general information. It is not a substitute for medical advice, and readers are admonished not to enact or change treatments based on this article. Always seek the advice of your doctor before starting or changing treatment.

The thoughts, views, and opinions expressed in this article are my own and do not reflect or represent the policy or position of Northeast Ohio Medical University.

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