From the Guidelines
To check for Graves' disease, the primary laboratory tests are thyroid stimulating hormone (TSH), free thyroxine (T4), and triiodothyronine (T3) levels, along with thyroid stimulating immunoglobulin (TSI) or thyroid receptor antibody (TRAb) tests. The TSH test is typically suppressed (low or undetectable) in Graves' disease, while free T4 and T3 levels are elevated 1. The TSI or TRAb test measures antibodies that stimulate the thyroid gland and are present in about 90-95% of patients with Graves' disease.
Additional helpful tests include:
- Thyroid peroxidase antibodies (TPOAb) and thyroglobulin antibodies (TgAb), which are often elevated in autoimmune thyroid conditions
- Complete blood count and comprehensive metabolic panel to assess overall health status and rule out other causes of symptoms
- Radioactive iodine uptake scan, which can help confirm the diagnosis by showing diffusely increased uptake throughout the thyroid gland
These tests together help differentiate Graves' disease from other causes of hyperthyroidism, such as toxic nodular goiter or thyroiditis 1. It is essential to note that the optimal screening interval for thyroid dysfunction is unknown, and the USPSTF found no direct evidence that treatment of thyroid dysfunction based on risk level alters final health outcomes 1. However, treatment is generally recommended for patients with a TSH level that is undetectable or less than 0.1 mIU/L, particularly those with overt Graves disease or nodular thyroid disease 1.
From the Research
Diagnostic Tests for Graves' Disease
To diagnose Graves' disease, several laboratory tests can be used, including:
- Measurement of serum levels of anti-TSH-receptor antibodies (TRAb) 2
- Thyroid ultrasonography 2
- Thyroid-stimulating hormone (TSH) test 3, 4
- Free T4 and free T3 assays to assess biological severity and monitor treatment efficacy 3
- Anti-TSH-receptor (TSH-R) antibody screening 3
- Scintigraphy in rare cases of Graves' disease with negative antibody findings or when another etiology is suspected 3
- Thyroid ultrasound scan, which may be contributive but is not recommended in first line 3
Laboratory Tests to Differentiate Graves' Disease from Other Thyrotoxicosis Causes
The following laboratory tests can help differentiate Graves' disease from other causes of thyrotoxicosis: