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TSI

Definition

TSI stands for thyroid stimulating immunoglobulin. TSI tells the thyroid gland to swell and release excess amounts of thyroid hormone into the blood.

This article discusses the test to determine the amount of TSI in your blood.

Alternative Names

TSH receptor antibody; Thyroid stimulating immunoglobulin

How the test is performed

A blood sample is needed. For information on how this is usually done, see: Venipuncture

How to prepare for the test

No special preparation is usually necessary.

How the test will feel

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed

Your doctor may order this test if you have signs or symptoms of:

The test is also done during the last 3 months of pregnancy to predict neonatal Graves disease.

Normal Values

Normal values are less than 130% of basal activity.

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

The example above shows the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.

What abnormal results mean

Greater than normal levels may indicate:

  • Graves disease
  • Hashitoxicosis
  • Neonatal thyrotoxicosis

What the risks are

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

  • Excessive bleeding
  • Fainting or feeling light-headed
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)

References

Kim M, Ladenson P. Thyroid. In: Goldman L, Schafer AI, eds. . 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 233.

Salvatore D, Davies TF, Schlumberger MJ, Hay ID, Larsen PR. Thyroid physiology and diagnostic evaluation of patients with thyroid disorders. In: Melmed S, Polonsky KS, Larsen PR,  Kronenberg HM, Larsen PR, eds. . 12th ed. Philadelphia, Pa: Saunders Elsevier;2011:chap 11.

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    Encyclopedia content is provided as information only and not intended to replace the advice and instruction from your personal physician.