Blood Tests for Thyroid Eye Disease

There are several blood tests your doctor may use to diagnose and monitor thyroid eye disease (TED). Certain substances may be present in the blood of people with TED. Blood tests will be ordered to check your thyroid hormone levels and help with diagnosing TED.

Thyroid-stimulating hormone (TSH)

Thyroid-stimulating hormone (TSH) is a hormone made in the pituitary gland of the brain. TSH tells the thyroid gland to make thyroid hormones. When thyroid hormone levels in your body are low, the pituitary gland makes more TSH. When TSH levels are high, the pituitary gland makes less TSH.^1-3

High TSH levels can mean a low-functioning thyroid, known as hypothyroidism. On the other hand, low TSH can mean your thyroid is making too much of the thyroid hormones. This is known as hyperthyroidism.^1,4

In 8 to 9 out of 10 cases, TED is caused by an overactive thyroid. Because of this, most people with TED will have low TSH levels.^1,4

Triiodothyronine (T3) and thyroxine (T4)

Triiodothyronine (T3) and thyroxine (T4) are hormones made in the thyroid but controlled by the pituitary gland in the brain. These are both typically high in those with Graves’ disease, an autoimmune disease that causes hyperthyroidism. Graves’ disease may occur with TED, but neither disease causes the other.^5,6

There are 2 forms of T3 and T4:^5,6

• Bound, which attaches to protein and does not enter the body tissues
• Free, which does not attach to anything and enters the body where it is needed

Because most people with TED have hyperthyroidism, T3 and T4 levels are usually increased. However, this does not always happen, so your TED specialist will use many different tests and exams to diagnose and manage the condition.^5,6

Thyroid-stimulating immunoglobulin (TSI)

Thyroid-stimulating immunoglobulin (TSI) is the antibody present in those with Graves’ disease. A positive result proves Graves’ disease. In Graves’ disease, the body makes TSI, which mimics TSH. This tricks the body into thinking it needs more thyroid hormone. The result is too much T3 and T4, which leads to hyperthyroidism.^5,6

Up to half of those with Graves’ disease develop TED. However, both TED and Graves’ are separate conditions requiring different treatment.⁷

Thyroid-stimulating hormone receptor antibody (TRAb)

Thyroid-stimulating hormone receptor antibody (TRAb) is another harmful antibody that may or may not be present in those with Graves’ disease.³

Anti-thyroid peroxidase antibody (anti-TPO)

Anti-thyroid peroxidase antibody (anti-TPO) is a harmful antibody that is usually found in those with Graves’ disease. This antibody is also found in people with Hashimoto’s disease. This is an autoimmune thyroid disease that leads to low thyroid function (hypothyroidism).³

Labs performed before and while taking TED medicines

If you will be taking medicines for TED, your TED specialist might order some lab tests before and during treatment. Some of these lab tests might include:²

• Complete blood count (CBC), which includes blood cell levels to check for a wide range of conditions, including anemia (low red blood cells) or infection (high white blood cells)
• Liver function tests, which measure the function and health of your liver
• Blood glucose test, which measures the amount of glucose (sugar) in your blood.

Talk to your doctor about the lab testing you might need for TED. Depending on your thyroid function, you might need multiple tests for diagnosing, treating, and monitoring TED.