TRAb stands for TSH receptor antibody. It's an antibody that binds to the TSH receptor on thyroid cells. These antibodies can stimulate or block the receptor, disrupting thyroid hormone production.
In more detail:
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TSH Receptor: The TSH receptor is a protein on the surface of thyroid cells that binds to thyroid-stimulating hormone (TSH). TSH normally stimulates the thyroid gland to produce thyroid hormones (T4 and T3).
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Antibodies: Antibodies are proteins produced by the immune system to fight foreign substances. In autoimmune diseases, the immune system mistakenly attacks the body's own tissues.
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TRAb in Graves' Disease: In Graves' disease, the most common cause of hyperthyroidism, TRAb acts like TSH and stimulates the thyroid gland to produce excessive amounts of thyroid hormones. This leads to the symptoms of hyperthyroidism, such as rapid heartbeat, weight loss, anxiety, and heat intolerance. TRAb is considered the gold standard diagnostic test for Graves' disease.
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Types of TRAb: There are different types of TRAb:
- Stimulating TRAb (TSI): These mimic TSH and activate the TSH receptor, leading to increased thyroid hormone production.
- Blocking TRAb (TBII): These block TSH from binding to the receptor, potentially leading to hypothyroidism. They are less common in Graves' disease but can occur.
- Neutral TRAb: These bind to the receptor but don't stimulate or block it.
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Clinical Significance: Measuring TRAb levels is crucial for:
- Diagnosing Graves' disease: Elevated TRAb levels are highly indicative of Graves' disease.
- Monitoring treatment: TRAb levels can be monitored during treatment to assess response.
- Predicting neonatal hyperthyroidism: In pregnant women with Graves' disease, TRAb can cross the placenta and affect the fetal thyroid, potentially causing neonatal hyperthyroidism.
Therefore, TRAb, or TSH receptor antibody, is a key indicator and diagnostic marker in autoimmune thyroid diseases, especially Graves' disease, reflecting an immune system attack on the thyroid's TSH receptor.
