Thyroid Antibodies

A thyroid antibody test measures the level of thyroid antibodies in a sample of your blood. Your thyroid is a small, butterfly-shaped gland in your neck. It makes hormones that control many activities in your body, including your heart rate and how fast you burn calories from food.

Antibodies are proteins that your immune system makes to fight foreign substances, such as viruses and bacteria. But sometimes antibodies attack the healthy cells of your own tissues and organs by mistake. This is called autoimmune disease.

If antibodies attack your thyroid, they can cause serious thyroid autoimmune diseases: Hashimoto's disease, also known as Hashimoto's thyroiditis, is the most common cause of hypothyroidism (underactive thyroid). Hypothyroidism happens when your thyroid doesn't make enough thyroid hormones to meet your body's needs. Thyroid hormones affect the way your body uses energy.

So, without enough thyroid hormones, many of your body's functions slow down.; Graves' disease is the most common cause of hyperthyroidism (overactive thyroid). With hyperthyroidism, your thyroid makes more thyroid hormones than your body needs. This causes many of your body's functions to speed up.; If your health care provider has diagnosed you with hypothyroidism or hyperthyroidism, thyroid antibody tests can help find out if a thyroid autoimmune disease is causing the problem.

There are different tests that check for different types of thyroid antibodies. Your provider will choose tests for you based on your symptoms, the results of other tests, and information about your medical history and family health history.

Why this test is done

You may need a thyroid antibody test if you have symptoms of Hashimoto's disease or Graves' disease. But first, your provider will usually order blood tests to check your thyroid hormone levels to see if you have hyperthyroidism or hypothyroidism. Thyroid hormone tests include T3, T4, and TSH (thyroid-stimulating hormone).

Sometimes these test results, along with your health history, your family, an exam, and your symptoms, are enough to make a diagnosis with thyroid antibody testing.

Symptoms of Hashimoto's disease include:

• Weight gain
• Fatigue
• Hair loss
• Low tolerance for cold temperatures
• Irregular menstrual periods
• Constipation
• Depression
• Joint pain

Symptoms of Graves' disease include:

• Weight loss
• Bulging of the eyes
• Tremors in the hand
• Low tolerance for heat
• Trouble sleeping
• Anxiety
• Increased heart rate
• Swollen thyroid, known as goiter

How to prepare

There are no special preparations necessary for a thyroid antibodies blood test.

Sample type

Blood

Other names for this test

thyroid autoantibodies, thyroid peroxidase antibody, TPO, anti-TPO, antithyroid microsomal antibody, thyroid- stimulating immunoglobulin, TSI, TSH receptor antibody, Long-acting thyroid stimulator, LATS, TSH receptor-binding inhibitory immunoglobulin, Human thyroid stimulator