What is the typical anti-thyroid peroxidase (anti-TPO) level in Hashimoto encephalopathy?

Anti-TPO Levels in Hashimoto Encephalopathy

Patients with Hashimoto encephalopathy typically have significantly elevated anti-TPO antibody levels, with mean values around 4,000 IU/mL (range 1,000-7,000 IU/mL), which are substantially higher than those seen in uncomplicated Hashimoto's thyroiditis. 1

Diagnostic Antibody Profile

Hashimoto encephalopathy (HE), also known as Steroid-Responsive Encephalopathy Associated with Thyroiditis (SREAT), is characterized by:

• Markedly elevated anti-TPO antibodies:

  • Mean values of approximately 4,043 ± 2,969 IU/mL in pediatric patients 1
  • Significantly higher than levels seen in patients with Hashimoto's thyroiditis without encephalopathy (1,980 ± 3,449 IU/mL) 1
  • Adult patients typically show similar patterns of elevation

• Anti-thyroglobulin antibodies (anti-Tg):

  • Often elevated but less consistently than anti-TPO
  • Reported levels around 74.6 IU/mL in some cases 2

Clinical Correlation with Antibody Levels

The relationship between antibody titers and clinical manifestations is complex:

• Anti-TPO antibodies are found in cerebrospinal fluid (CSF) of HE patients but not in patients with other neurological disorders 3
• These antibodies bind to cerebellar astrocytes, suggesting a direct pathogenic role 3
• High antibody levels do not necessarily correlate with disease severity
• Antibody reduction (even to undetectable levels) through plasma exchange doesn't always result in clinical improvement 4

Clinical Presentation Associated with Elevated Anti-TPO

Patients with elevated anti-TPO antibodies and HE commonly present with:

• Cognitive impairment and behavioral changes (76.9% of cases) 5
• Sleep disturbances (69.2%) 5
• Seizures (46.1%) 5
• Psychosis or paranoia (38.5%) 5
• Transient neurological symptoms (46.1%) 5
• Myoclonus (30.8%) 5
• Ataxia or gait disorders (30.8%) 5

Diagnostic Considerations

When evaluating a patient with suspected HE:

• Anti-TPO antibodies should be measured in all patients with unexplained encephalopathy 5
• Normal thyroid function tests do not rule out HE (75% of pediatric HE patients had normal T4 and TSH levels) 1
• CSF protein is frequently elevated (88.8% of cases) 5
• EEG abnormalities are common (53.8% of cases) 5
• MRI findings are less consistent (abnormal in only 15.4% of cases) 5

Treatment Response and Prognosis

• Most patients (>80%) show excellent response to steroid therapy 5
• Despite treatment, relapses are common, particularly in pediatric patients 1
• Some patients may require additional immunosuppressive therapy
• Hashimoto encephalopathy can evolve into Hashimoto's thyroiditis, but the reverse is rare 1

Pitfalls and Caveats

1. Anti-TPO levels alone cannot diagnose HE; clinical correlation is essential
2. Normal thyroid function does not exclude HE
3. Anti-TPO levels may not correlate with treatment response
4. HE should be considered in the differential diagnosis of any unexplained encephalopathy
5. Early recognition and treatment are crucial for preventing long-term neurological sequelae

The diagnosis of Hashimoto encephalopathy requires a high index of suspicion, as it is a diagnosis of exclusion after ruling out infectious, neoplastic, toxic, and metabolic causes of encephalopathy.