What is Hashimoto's Encephalopathy?

By SWA

Hashimoto’s Encephalopathy (HE) is a rare, often misunderstood neurological disorder associated with autoimmune thyroid disease, especially Hashimoto’s thyroiditis. It is not directly caused by abnormal thyroid hormone levels, but rather by an autoimmune reaction that appears to affect the brain.

Autoimmunity and the Thyroid Gland

Hashimoto’s thyroiditis is an autoimmune condition in which the body’s immune system attacks the thyroid gland. This leads to chronic inflammation and, over time, impaired thyroid hormone production (hypothyroidism). In some cases, however, brain symptoms arise independently of hormone levels — this is known as Hashimoto’s Encephalopathy.

What Is Hashimoto’s Encephalopathy?

HE — also called Steroid-Responsive Encephalopathy Associated with Autoimmune Thyroiditis (SREAT) — is characterized by a wide range of neurological and psychiatric symptoms. These symptoms are believed to result from autoimmune inflammation in the brain, not directly from thyroid hormone imbalance.

Common Symptoms of Hashimoto’s Encephalopathy

Symptoms can develop gradually or come on suddenly, and may include:

  • Cognitive impairment: memory loss, confusion, difficulty concentrating

  • Sleep disturbances: excessive daytime sleepiness or insomnia

  • Psychiatric symptoms: hallucinations, delusions, mood swings, personality changes

  • Neurological signs: seizures, tremors, myoclonus (muscle jerks), ataxia (coordination problems)

  • Visual disturbances: blurred vision, double vision

  • Speech difficulties: slurred or slowed speech

Diagnosis

Diagnosing HE involves ruling out other causes of encephalopathy (e.g., infection, metabolic imbalance, stroke). Key diagnostic clues include:

  • Elevated anti-thyroid antibodies (especially anti-TPO antibodies)

  • Normal or abnormal thyroid hormone levels (TSH, T3, T4)

  • EEG showing slow brain wave activity

  • MRI may be normal or show nonspecific changes

  • Dramatic improvement with corticosteroid therapy (prednisone) supports the diagnosis

Role of Iodine and Iodine Tablets

Iodine is a critical nutrient for thyroid hormone production, but its role in autoimmune thyroid disease is complex:

  • In Hashimoto’s thyroiditis, too much iodine (from supplements or tablets) may worsen the autoimmune attack on the thyroid.

  • Although iodine imbalance can influence thyroid function, there is no direct link between iodine intake and Hashimoto’s Encephalopathy.

  • In some sensitive individuals, iodine tablets may trigger or aggravate autoimmune symptoms, so iodine intake is often monitored or restricted.

What About the Nebenschilddrüsen (Parathyroid Glands)?

The parathyroid glands (Nebenschilddrüsen) are four small glands located behind the thyroid. Despite their location, they have a different function:

  • Parathyroid glands regulate calcium and phosphate levels in the blood via parathyroid hormone (PTH).

  • They are not directly involved in Hashimoto's thyroiditis or encephalopathy.

  • However, parathyroid disorders (like hyperparathyroidism) can also cause neurological symptoms — including confusion, fatigue, depression, and memory issues — and may mimic or complicate the diagnosis of HE.

  • It’s important for doctors to check calcium and PTH levels to rule out parathyroid-related causes when evaluating a patient for encephalopathy.

    Key Difference:

    Thyroid (Schilddrüse)
    Parathyroid (Nebenschilddrüse)
    Controls metabolism via thyroid hormones
    Controls calcium/phosphate via PTH
    Affected in Hashimoto's encephalopathy
    Not directly involved in HE
    Autoimmune diseases common
    Autoimmune disease less common

Treatment of Hashimoto’s Encephalopathy
The good news is that HE usually responds very well to treatment:

  • Corticosteroids (like prednisone) are the mainstay therapy and often lead to rapid improvement.

  • If steroids fail, other immunosuppressants (e.g., azathioprine, IVIG) may be used.

  • Managing thyroid hormone levels is also important — for example, levothyroxine if the patient is hypothyroid.

  • Any parathyroid dysfunction should be ruled out or treated separately if present.

Summary Table

AspectDetails
CauseAutoimmune brain inflammation associated with thyroid autoimmunity
Thyroid functionMay be normal, low, or high
SymptomsCognitive issues, psychiatric changes, neurological problems, vision issues
DiagnosisAntibodies, EEG, response to steroids, exclusion of other causes
IodineMay worsen thyroid autoimmunity in some cases
NebenschilddrüsenNot directly involved, but disorders may mimic HE symptoms
TreatmentSteroids, immunosuppressants, thyroid hormone correction

Reference:
Hashimoto's encephalopathy: Follow‐up data from neuropsychology, lumbar puncture, and FDG‐PET https://pmc.ncbi.nlm.nih.gov/articles/PMC6745505/

Hashimoto's encephalopathy:
https://www.encephalitis.info/types-of-encephalitis/autoimmune-encephalitis/hashimotos-encephalopathy/

Parathyroid Disorders:
https://medlineplus.gov/parathyroiddisorders.html

 

© 2000-2025 Sieglinde W. Alexander. All writings by Sieglinde W. Alexander have a fife year copy right.
Library of Congress Card Number: LCN 00-192742 ISBN: 0-9703195-0-9

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