Graves’ disease is the most common form of hyperthyroidism or overactive thyroid. The thyroid gland controls your body’s metabolism — how your body uses energy.
Thyroid hormones are vital for every cell in your body. When the thyroid gland is overactive and makes too many hormones, your body’s metabolism runs too fast. You end up with symptoms such as feeling too hot, weight loss, nervousness, and sleep problems.
The disease is most common in people assigned female at birth. Risk factors include using nicotine, having a family history of thyroid diseases, and having an autoimmune disorder.
The main treatments are antithyroid medications, radioactive iodine, and surgery.
Radioactive iodine and surgery may cure Graves’ disease. However, you may need thyroid hormone replacement for the rest of your life. Healthcare professionals often prefer trying antithyroid medications first for people with mild disease who are more likely to go into remission.
The role of antibodies in Graves’ disease
Graves’ disease is an autoimmune disorder, meaning your immune system attacks the body’s tissues.
Normally, the immune system fights germs and toxins by making antibodies. These are special proteins that attach to the invader, which helps the body get rid of it.
With autoimmune disorders, the immune system makes antibodies that bind to healthy tissues. Most of the time, it is unclear why this occurs.
With Graves’ disease, the immune system makes an antibody that binds to a receptor on the thyroid gland. Usually the thyroid-stimulating hormone (TSH) binds to this receptor. TSH does just what its name says, it stimulates the thyroid gland to make thyroid hormone.
The body has a feedback system that slows the thyroid gland once it has made enough thyroid hormone. TSH levels fall as the thyroid makes its hormones.
Less TSH means less stimulation of the thyroid to make hormones. If thyroid hormone levels get too low, TSH levels go up. This tells the thyroid gland it is time to make more thyroid hormone.
The antibodies in Graves’s disease constantly bind to the TSH receptor. This causes the thyroid gland to keep making thyroid hormone even though it does not need to.
Types of antibodies in Graves’ disease
The main antibody in Graves’ disease is thyroid stimulating hormone receptor antibody (TSHR Ab or TRAb). TRAb binds to the thyroid gland and stimulates it to make thyroid hormone.
This is the underlying cause of Graves’ disease. When doctors test for this antibody, it is high in 95% of people with Graves’ disease.
The level of TRAb can tell doctors about the severity of Graves’ disease. Very high levels at diagnosis often means it will be hard to control the disease long term with only medications.
Doctors may also check TRAb levels to monitor treatment, such as before stopping medications.
The other antibody that can be high in Graves’ disease is thyroid peroxidase antibody (TPOAb). This antibody binds to an enzyme the thyroid gland makes.
About 70% of people with Graves’ disease will have high levels of TPOAb. Doctors usually order this test just once at diagnosis. The National Institutes of Health (NIH)suggests TPOAb is more more common in people living with Hashimoto’s thyroiditis and may lead to developing hypothyroidism.
These are also called antibody tests thyroid stimulating antibodies (TSI), or thyroid autoantibodies.
It is possible to have antibody tests come back negative and still have Graves’ disease. If these tests are negative, doctors may recommend a thyroid scan to reach a diagnosis.
This test will show how the thyroid gland takes up iodine. In Graves’ disease, doctors see iodine throughout the thyroid gland and not in just some places.
It is also possible to have positive thyroid antibody tests but not have thyroid disease. This happens in about 10% of people and increases the risk of developing thyroid disease later.
Questions to ask your doctor
If your doctor has recommended thyroid antibody testing, here are some questions you could ask:
- What will my thyroid antibody level tell you about my diagnosis and prognosis?
- Can my results help guide my treatment options?
- Will thyroid antibodies ever go away?
- Will I need follow up thyroid antibody testing in the future?
- What other follow up testing do I need, such as a thyroid scan or testing for other autoimmune disorders?
With proper treatment, Graves’ disease is manageable. You and your doctor can use your thyroid antibody test results to choose the best way forward for you.