TRAb Test
The TRAb (TSH receptor antibody) test detects antibodies that stimulate the thyroid — the specific marker for Graves’ disease, the most common cause of hyperthyroidism.
It distinguishes Graves’ from other causes of thyrotoxicosis.
Last medically reviewed: 1 November 2025
What it measures
TRAb antibodies bind to and activate the TSH receptor on thyroid cells — mimicking TSH and driving continuous hormone production. Different assays measure stimulating vs blocking antibodies.
Positive TRAb is highly specific for Graves’ disease.
When it is ordered
TRAb is checked when hyperthyroidism is diagnosed to identify Graves’ vs toxic nodules or thyroiditis. It helps predict relapse risk after antithyroid drugs are stopped — persistent positive TRAb suggests higher relapse likelihood.
It may also be monitored in pregnancy for neonatal risk assessment.
Interpretation
Positive TRAb confirms Graves’ disease. Negative TRAb in thyrotoxicosis suggests alternative causes — toxic nodules, thyroiditis, or factitious thyrotoxicosis.
TRAb levels correlate loosely with disease activity; very high levels may predict more severe disease or eye involvement.
Frequently asked questions
Can TRAb be positive without hyperthyroidism?
Yes — low-level TRAb positivity can occur in euthyroid people or during remission. Clinical context and thyroid function tests are needed.
Does TRAb predict relapse after treatment?
Persistently positive TRAb after antithyroid drugs are stopped is associated with higher relapse risk — one factor in deciding whether to continue, switch, or stop treatment.
Is TRAb the same as TSH?
No — TRAb is an antibody that mimics TSH’s effect; TSH is the pituitary hormone. In Graves’, TRAb drives the thyroid while TSH is suppressed.
References & further reading
This page is based on established medical knowledge and guidelines from authoritative sources. Always consult a qualified clinician for personal medical advice.
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