Diagnosing Graves disease is a straightforward process when symptoms like goiter or protruding eyes are present. However, 50% of people with Graves disease may not have obvious signs and symptoms and laboratory tests are required for diagnosis. Testing is done to evaluate the health of the thyroid, diagnose Graves disease, and monitor treatment.
To determine whether the thyroid is functioning properly, testing may begin with:
- Thyroid-stimulating hormone (TSH) — typically low in Graves disease
- Free T4 — usually elevated
- Free and Total T3 — often elevated
The above tests may also be ordered periodically to monitor thyroid function and hormone production.
Laboratory tests used to help diagnose Graves disease and distinguish it from other autoimmune conditions may include one or more of the following. These tests detect the presence of thyroid antibodies:
- Thyroid stimulating immunoglobulin (TSI) — presence of this antibody is diagnostic for Graves disease
- Thyroid stimulating hormone receptor antibody (TRAb) — less specific than TSI
- Anti-thyroid peroxidase antibody (anti-TPO) — this autoantibody is found in most people with Graves disease as well as in Hashimoto thyroiditis
- Radioactive iodine uptake — For this test, a capsule or "cocktail" containing a measured amount of radioactive iodine is swallowed; iodine is a critical component of thyroid hormones. The iodine accumulates in the thyroid; more accumulates when the gland is overactive, as occurs in Graves disease. After a specified amount of time, a probe similar to a Geiger counter is placed over the thyroid and the amount of radioactivity is compared to the amount that was given. For additional details, visit RadiologyInfo.org.
- Ultrasound may be used for people who can't undergo radioactive iodine uptake to see if the thyroid gland is enlarged.