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Thyroid Peroxidase Antibodies
(a.k.a TPO)
minimum sample volume required ~ 0.5ml
Test Code: TPO
Special instructions
Tube type: SST
Sent away
to Southmead Hospital
Reference range
<22
Units
IU/mL
Turnaround Time
14
days
Department: Immunology
Clinical Application
TPO antibodies are directed against thyroid peroxidase (TPO) and can interfere with TPO function, which includes production of thyroid hormones, T3 and T4, via iodination and coupling of tyrosine residues. TPO antibodies are present in 90% of patients with autoimmune hypothyroidism (Hashimoto’s disease) and in 10% of those without thyroid disease.
Measurement of TPO antibodies is recommended under limited scenarios:
1. Risk of hypothyroidism in pregnancy (or pre-conception).
2. Children with subclinical or overt thyroid disease.
3. Complex Endocrinology patients.
TPO antibody status plays no role in determining thyroxine replacement in hypothyroid patients, or in non-pregnant patients with borderline thyroid function (TFT) abnormalities. Clinicians should be guided by TSH/FT4 levels and any symptoms.
In those with subclinical hypothyroidism, we no longer recommended measurement of TPO. Instead, annual TFTs should be performed, unless otherwise indicated.
Webpage updated: September 2024.
