Alternative Names thyroid stimulating immunoglobulin, LATS, TSIG, long-acting thyroid stimulator
Definition This test measures the level of TSH receptor antibody in the blood. A doctor can use this test to find out what is causing hyperthyroidism, also known as Graves' disease. Hyperthyroidism occurs when too much thyroid hormone is secreted by the thyroid gland. When this happens, the body's metabolic rate increases to abnormally high levels.
TSH receptor antibody is an antibody that binds to special receptor sites on the thyroid gland that normally bind to the thyroid stimulating hormone, TSH. TSH is the hormone that stimulates the thyroid gland to secrete thyroid hormone. TSH receptor antibody mimics the effect of TSH, thereby causing the thyroid to secrete excess thyroid hormone.
Who is a candidate for the test? This test is normally performed to diagnose and evaluate suspected thyroid disease. It may also be used to monitor treatment of certain thyroid disorders.
How is the test performed? To measure the amount of TSH receptor antibody in the blood, a blood sample is taken from a vein on the forearm or hand. First, the skin over the vein is cleaned with an antiseptic. Next, a strong rubber tube, or "tourniquet," is wrapped around the upper arm. This enlarges the veins in the lower arm by restricting blood flow through them. A fine needle is gently inserted into a vein, and the tourniquet is removed. Blood flows from the vein through the needle, and is collected in a syringe or vial for testing in the laboratory. After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.
What is involved in preparation for the test? A person should request specific instructions from his or her doctor.
What do the test results mean? Normally, there is no TSH receptor antibody in the blood. If TSH receptor antibody is found in the blood, this usually indicates that the TSH receptor antibody is the cause of the of a person's hyperthyroidism.
Author: David T. Moran, MD Reviewer: eknowhow Medical Review Panel Editor: Dr John Hearne Last Updated: 6/06/2005 Contributors Potential conflict of interest information for reviewers available on request
