Graves Disease Diagnosis: Tests for Antibodies, Hormones and RAIU

Graves’ disease is diagnosed through your history, symptoms, physical signs, and by performing certain blood and imaging tests.

You should know that Graves’ is an autoimmune disease and such diseases are known to have a genetic and familial trait. The immune system produces antibodies against the tissues of the body itself causing an autoimmune condition.

History and physical signs

The doctor will inquire about any personal or family history of any autoimmune disease such as type 1 diabetes, rheumatoid arthritis, pernicious anemia or vitiligo.

Graves’ disease is an autoimmune disorder and any past history suggestive of an autoimmune disease in you or your family will be highly suggestive of the thyroid enlargement being due to Graves’.

The doctor will ask you questions about your symptoms and will conduct a physical exam and take your vital statistics.

He will check your thyroid gland for any symmetrical enlargement in size. He will look for fine tremors in your hands and fingers. He will look for signs of tachycardia (rapid heart rate) and for any rise in blood pressure.

Graves’ eye disease (exophthalmus) and Graves’ dermopathy are giveaway signs.

Thyroid function tests are tests that measure the amount of TSH and thyroid hormones in the blood. They include;

  • Thyroid stimulating hormone (TSH) secreted by the pituitary gland and which regulates thyroid hormone production and secretion.
  • Thyroid hormones T3 and T4 (Total T3 and T4)
  • Free T4

In Graves’ disease, antibodies produced by the immune system are also measured because Graves’ is an autoimmune disease.

Radioactive iodine uptake by the thyroid gland is also measured to know the amount of iodine taken up by the thyroid and determine how much of the gland is active.

Thyroid antibody titers

Blood tests are carried out to measure thyroid stimulating immunoglobin (TSI) and TSH receptor antibodies’ (TRAb) levels, which show that they are very high in Graves’ hyperthyroidism.

High levels of these antibodies confirm the diagnosis of Graves’ disease and no further testing is then needed.

Graves’ is an autoimmune disease in which the immune system in the body produces these antibodies that attack the thyroid gland causing this condition.

If the values of the antibodies are not raised, then the doctor will ask for a radioactive iodine uptake test (RAIU) to clinch the diagnosis.

A high serum TRAb level measurement during pregnancy is a high-risk factor for intrauterine death, premature delivery, and fetal or neonatal hyperthyroidism.

Blood test for total T3, T4, and TSH

In Graves’ disease, TSH levels will be below normal, T4 levels may be slightly raised and T3 levels will definitely be elevated. This is because the antibody thyroid-stimulating immunoglobulins (TSI antibodies) are misdirecting the thyroid into making too much T3 and T4.

Due to the high levels of T3 and T4, the pituitary stops secreting TSH to discourage the thyroid from making more thyroid hormones. Therefore, TSH levels will be low.

Testing free T4

A free T4 test is a more recent test and gives a more accurate picture of T4 levels. It is run if the TSH level is not normal.

This test is more accurate because the blood proteins can bind to the total T4 and give an inaccurate picture of thyroid function. A free T4 is not affected by the blood proteins.

Radioactive Iodine Uptake (RAIU)

A radioactive iodine uptake test is done in the medical center’s nuclear imaging department.

The procedure involves taking an iodine pill called a radioactive tracer four to six hours before your thyroid gland is first scanned.

It measures the quantity of iodine the thyroid takes up and also informs whether the whole thyroid or part of it is hyperactive.

Another scan is usually repeated after 24 hours. The amount of iodine the thyroid absorbs tells the doctor whether the thyroid is normal or abnormal.

In hyperthyroidism caused by Graves’ disease, the thyroid scan shows an increased uptake of iodine over the entire thyroid gland.

Orbital imaging

If you develop exophthalmus, orbital imaging may be done in order to define the exact impact of Graves’ disease on the eyes and surrounding structures (e.g. orbital muscles).

This includes CT scan, MRI, or ultrasound (echography) of the eyes and eye sockets.