TSH Receptor Antibody

Function

TSH Receptor Antibodies (TRAb) are autoantibodies that bind to the thyroid-stimulating hormone (TSH) receptors on the thyroid gland. These antibodies can either stimulate the receptor (causing hyperthyroidism) or block the receptor (causing hypothyroidism). The most common form of TRAb is Thyroid Stimulating Immunoglobulin (TSI), which mimics the action of TSH, leading to the overproduction of thyroid hormones.

Why it is Ordered

This test is primarily ordered to confirm a diagnosis of Graves' disease in patients with symptoms of hyperthyroidism, such as rapid heartbeat, weight loss, and bulging eyes (exophthalmos). It is also used to differentiate Graves' disease from other forms of thyrotoxicosis, such as toxic multinodular goiter or thyroiditis. In pregnant women with a history of Graves', TRAb is measured to assess the risk of neonatal thyrotoxicosis, as these antibodies can cross the placenta.

Associated Conditions

The primary condition associated with elevated TRAb is Graves' Disease, an autoimmune disorder that is the most common cause of hyperthyroidism. High levels are also linked to Graves' Ophthalmopathy (eye involvement). In some cases of Atrophic Thyroiditis or Hashimoto's Thyroiditis, 'blocking' antibodies (a subset of TRAb) may be present, contributing to a hypothyroid state.