TSH Receptor Antibody (TRAb) Test

This test measures TSH receptor binding antibodies in serum with an ELISA that detects how strongly the antibodies inhibit TSH binding to its receptor. Results are reported in IU/L; Quest's reference value is 2.00 IU/L or less. Because it is a binding assay, it detects stimulating and blocking antibodies together without telling them apart.

People whose TSH and free T4 show hyperthyroidism and whose clinician wants to confirm or exclude Graves' disease; people with symptoms such as a racing heart, tremor, heat intolerance, weight loss or eye changes; people with Graves' disease considering stopping antithyroid medicine with their clinician; and pregnant or postpartum people with thyroid problems, as directed by their clinician.

After thyroid function tests suggest an overactive thyroid and the cause is unclear, before stopping antithyroid medicine (normal levels suggest a better chance of remission), and at the pregnancy time points your clinician follows (the ATA uses the first trimester or first visit, 18-22 weeks, and 30-34 weeks depending on history). No fasting is needed.

A result at or below Quest's reference value (2.00 IU/L or less) means TSH receptor antibodies were not detected at a significant level, which makes Graves' disease less likely, though the ATA notes TRAb can be negative in very mild disease. An elevated result in someone with hyperthyroidism strongly supports Graves' disease. Because this binding test also detects blocking antibodies, an elevated result in someone with an underactive thyroid can reflect blocking antibodies; Quest lists neonatal hypothyroidism and postpartum thyroid dysfunction among its uses. If the cause needs clarifying, a clinician may add the TSI bioassay. Review your result with a clinician or endocrinologist alongside TSH, free T4 and free T3. JustLabs results are informational and are not a diagnosis.