TSH-receptor antibody (TRAb / TSI)
An antibody test that confirms Graves' disease — the commonest cause of an overactive thyroid. These antibodies switch on the thyroid's TSH receptor, driving it to overproduce hormone. A positive result pins the diagnosis and helps guide treatment and pregnancy monitoring.
What it measures
The thyroid is normally controlled by the pituitary hormone TSH, which acts on a receptor on thyroid cells. In Graves' disease — an autoimmune condition and the commonest cause of an overactive thyroid (hyperthyroidism) — the body makes antibodies that bind and switch on this same TSH receptor, tricking the thyroid into overproducing hormone regardless of the body's actual needs. This test detects those antibodies (reported as TRAb, or as the stimulating subtype TSI). Its main use is to confirm that a case of hyperthyroidism is caused by Graves' disease rather than another cause such as a toxic nodule or thyroiditis — which matters because the causes are managed differently. A positive result strongly supports Graves' disease, often making a radioactive scan unnecessary. The test has two further important roles: the antibody level helps gauge the chance of the disease relapsing after a course of anti-thyroid medication, and — critically — it is checked in pregnancy, because these antibodies cross the placenta and, if high, can affect the baby's thyroid, so the level guides monitoring of mother and baby.
What a high value can mean
- A positive result — confirms Graves' disease as the cause of an overactive thyroid.
- Graves' disease with eye involvement (thyroid eye disease) — antibody levels are often higher.
- A guide to relapse risk — a high level after anti-thyroid treatment suggests a greater chance the overactivity returns.
- Important in pregnancy — a high level can affect the baby's thyroid, so it guides monitoring.
What a low value can mean
- A negative result — makes Graves' disease unlikely; an overactive thyroid is then more likely due to another cause (a toxic nodule, or thyroiditis).
- A falling level on treatment — can suggest the autoimmune process is settling.
When to discuss with a doctor
The TSH-receptor antibody test is used when the thyroid is found to be overactive, to confirm whether Graves' disease is the cause — which directs treatment. A positive result establishes the diagnosis; a negative one points toward other causes that are managed differently. The antibody level also helps judge the likelihood of relapse after a course of medication, and it has a specific and important use in pregnancy, where a high level means the baby's thyroid should be monitored because the antibodies cross the placenta. This is interpreted by endocrinology alongside the thyroid hormone levels. Mediora.AI surfaces the TRAb result alongside TSH and the thyroid hormones so the Graves' pattern is visible; the diagnosis, treatment choice and any pregnancy monitoring belong with your doctor.