What Do Elevated Thyroid Antibodies and Normal TSH Mean?

Understanding Autoimmune Hashimoto's Thyroiditis and Graves' Disease

thyroid antibodies, TPO, TSI, thyroid peroxidase antibodies, thyroid stimulating immunoglobulins
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If your doctor has told you that you have elevated thyroid antibodies, but at the same time you have a normal thyroid stimulating hormone (TSH) level, what does that specifically mean as far as your thyroid condition?

What are Antibodies?

Antibodies are proteins produced by your body that respond to or attempt to destroy antigens, substances such as viruses and bacteria that the body identifies as foreign.

In some cases, your body mistakenly identifies your own glands, tissues, and organs as foreign. This type of reaction is a characteristic of autoimmune disease, and these antibodies are called autoimmune antibodies.

What Type of Antibodies Do You Have?

An important first step is to determine which type of antibodies are elevated. If you have elevated thyroid peroxidase (TPO) antibodies, that may point to the autoimmune thyroid disease known as Hashimoto’s thyroiditis. If you have elevated thyroid stimulating immunoglobulins (TSI), you may have autoimmune Graves’ disease.

Do You Have Elevated Thyroid Peroxidase (TPO) Antibodies?

If you have elevated TPO antibodies, even if your TSH level is normal, you most likely have Hashimoto's thyroiditis, an autoimmune disorder. In Hashimoto’s thyroiditis, the TPO antibodies attack your thyroid gland.

Over time, the TPO antibodies cause inflammation and eventually can destroy all or part of your thyroid gland.

As the thyroid becomes less able to produce thyroid hormone, you become hypothyroid. Hashimoto’s antibodies can also cause your thyroid to form nodules, or become enlarged, known as goiter.

It can take time for the destructive effect on your thyroid to be reflected in your TSH test level. It is not uncommon, in fact, to have elevated antibodies for months or years before your TSH level rises to a point where you are diagnosed with hypothyroidism.

Meanwhile, it is also common for people with Hashimoto’s thyroiditis but normal TSH levels to have some hypothyroidism symptoms, which can include fatigue, weight gain, mood changes, brain fog, and recurrent miscarriage, among others.

Do You Have Elevated Thyroid Stimulating Immunoglobulins (TSI)?

If you have elevated TSI antibodies, even if your TSH level is normal, you most likely have Graves’ disease, an autoimmune condition.  In Graves’ disease, the TSI antibodies cause your thyroid gland to make too much thyroid hormone. As TSI antibodies cause overproduction of thyroid hormone, a TSH in the reference range drops, and you can become hyperthyroid fairly quickly.

What Does Euthyroid Mean?

The term euthyroid means that your TSH test result falls within the reference range. From a conventional perspective, this means you are neither hypothyroid or hyperthyroid, and even if TPO or TSI antibodies are elevated, treatment is not warranted.

The Controversy Over Treating Thyroid Antibodies

As noted, many conventional physicians and endocrinologists believe that when your TSH is within the reference range and you are euthyroid, but you have elevated thyroid antibodies, your condition does not require treatment.

This is controversial, however, as research shows that the presence of thyroid antibodies alone can cause symptoms of hypothyroidism or hyperthyroidism.

With elevated TSI, there is usually a short period between the onset of elevated antibodies, and a TSH level that reflects hyperthyroidism. If you are experiencing acute symptoms of hyperthyroidism—such as elevated blood pressure or heart rate, or substantial weight loss—your doctor is likely to start treatment.

TPO antibodies can be elevated for longer periods before the TSH level shows hypothyroidism, so there are two different approaches your doctor may take toward treating Hashimoto’s thyroiditis.

  1. Some doctors recommend a “wait and see,” approach, monitoring your TSH over time, and starting treatment only when your TSH goes above the reference range, typically a level above 4.0 to 5.0.
  2. If you have hypothyroidism symptoms, some endocrinologists, as well as holistic and integrative physicians, will prescribe a trial of thyroid hormone replacement medication, even when your TSH is within the reference range.

While it remains a controversy, if you have elevated TPO antibodies and a normal TSH level, there is evidence that thyroid hormone replacement treatment may have benefits for you, including:

  • You may experience full or partial relief of your hypothyroidism symptoms
  • Your antibody levels and inflammation in your thyroid gland may be reduced
  • The autoimmune process destroying your thyroid may be slowed or stopped
  • If your thyroid is enlarged (goiter), the size of your gland may be reduced
  • The treatment may prevent you from progressing to overt hypothyroidism

An Important Note Regarding Pregnancy

Research has shown that elevated TPO antibodies can triple the rate of miscarriage, and double the risk of preterm birth. While researchers are still studying the effects and potential benefits, some practitioners routinely prescribe thyroid treatment for pregnant women with elevated thyroid antibodies.

A Word from Verywell

If you have thyroid symptoms, but your TSH test result falls within the reference range, an important next step is to request that your doctor order thyroid antibody tests. If your symptoms suggest hypothyroidism—i.e., fatigue, weight gain, depression, hair loss—you should request a TPO antibody test. If your symptoms suggest hyperthyroidism—i.e., anxiety, insomnia, weight loss, diarrhea, elevated heart rate/blood pressure—you should request a TSI antibody test.

Sources:

Braverman, L, Cooper D. Werner & Ingbar's The Thyroid, 10th Edition. WLL/Wolters Kluwer; 2012.

Fröhlich, E., Wahl, R. "Thyroid Autoimmunity: Role of Anti-thyroid Antibodies in Thyroid and Extra-Thyroidal Diseases." Frontiers in Immunology. 2017; 8: 521. Published online 2017 May 9.

Garber, J, Cobin, R, Gharib, H, et. al. "Clinical Practice Guidelines for Hypothyroidism in Adults: Cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association." Endocrine Practice. Vol 18 No. 6 November/December 2012.

Kent, Athol. “Thyroid Antibodies Associated With Miscarriage and Preterm Birth.” Reviews in Obstetrics and Gynecology 4.3-4 (2011): 128–129. 2011.

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