Antithyroglobulin antibody

Alternative names
Thyroid antithyroglobulin antibody; Thyroglobulin antibody

Definition
Antithyroglobulin antibody is a test to measure antithyroglobulin antibodies in the blood. Thyroglobulin is a protein that is present in thyroid cells. (See “Why the test is performed.”)

How the test is performed

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a band or blood pressure cuff is placed around the upper arm to apply pressure and cause the veins below the band to swell.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children:
The area is cleaned with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. A bandage may be applied to the puncture site if there is any continued bleeding.

How to prepare for the test
Fasting may be required. Usually, you will be asked to refrain from eating (and sometimes drinking) overnight. Medications that may interfere with correct results will be monitored or discontinued until after the test.

Infants and children:
The preparation you can provide for this test depends on your child’s age, previous experiences, and level of trust. For general information regarding how you can prepare your child, see the following:

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
This test helps to detect possible thyroid problems. Thyroglobulin is a protein that is normally confined to the thyroid gland. It is the source of the thyroxine and triiodothyronine hormones in the body. The presence of autoantibodies to thyroglobulin can lead to the destruction of the thyroid gland. Such antibodies are more likely to appear after trauma to, or inflammation of, the thyroid gland.

Normal Values

A negative test is normal. In other words, no antibodies to thyroglobulin are detected.

What abnormal results mean

A postive test (where antibodies are detected) may be due to:

     
  • Hashimoto’s thyroiditis  
  • Thyrotoxicosis  
  • Systemic lupus erythematosus (SLE)  
  • Hypothyroidism  
  • Thyroid carcinoma  
  • Myxedema  
  • Grave’s disease  
  • Type 1 diabetes

Pregnant women and relatives of patients with autoimmune thyroiditis may also test positive for these antibodies.

What the risks are

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

Special considerations
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.

Johns Hopkins patient information

Last revised: December 7, 2012
by Sharon M. Smith, M.D.

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