From the Guidelines
To diagnose Graves' disease, the most critical laboratory tests to order are thyroid-stimulating hormone (TSH), free thyroxine (free T4), and free triiodothyronine (free T3), along with thyroid-stimulating immunoglobulins (TSI) or thyroid-stimulating hormone receptor antibodies (TRAb) as specific markers for the disease. According to the U.S. Preventive Services Task Force recommendation statement published in the Annals of Internal Medicine 1, the serum TSH test is the primary screening test for thyroid dysfunction, which includes hyperthyroidism caused by Graves' disease.
Key Laboratory Tests
- TSH: Typically suppressed (low or undetectable) in Graves' disease
- Free T4 and Free T3: Elevated levels
- TSI or TRAb: Positive results are specific markers for Graves' disease
- Thyroid peroxidase antibodies (TPO) and thyroglobulin antibodies (TgAb): Often elevated in autoimmune thyroid conditions, including Graves' disease
Rationale
The rationale behind these tests is to confirm the presence of hyperthyroidism and to differentiate Graves' disease from other causes of hyperthyroidism. The presence of TSI or TRAb is particularly important as these antibodies are directly involved in the pathogenesis of Graves' disease by stimulating the thyroid gland to produce excess thyroid hormones 1.
Additional Tests
Additional tests such as complete blood count and liver function tests may be ordered to assess the patient's overall health status and to rule out other causes of symptoms. However, for the diagnosis of Graves' disease, the focus should be on the thyroid function tests and the specific autoimmune markers.
From the Research
Labs to Check for Graves' Disease
To diagnose Graves' disease, several laboratory tests can be used, including:
- Thyroid-stimulating hormone (TSH) receptor antibodies (TRAb) test, which is considered the gold standard diagnostic test for Graves' disease 2
- Thyroid function tests, such as free triiodothyronine (fT3) and free thyroxine (fT4) levels, to evaluate the severity of hyperthyroidism 3
- Thyroid ultrasound, which is a sensitive imaging tool for diagnosing Graves' disease 4
- Measurement of thyrotropin receptor antibodies (TSH-R-Abs), which is a specific biomarker for Graves' disease 4
Diagnostic Criteria
The diagnosis of Graves' disease is based on a combination of clinical and laboratory findings, including:
- Presence of hyperthyroidism, which can be confirmed by elevated fT3 and fT4 levels 3
- Presence of TRAb, which is a specific marker for Graves' disease 2
- Thyroid ultrasound findings, which can show a characteristic pattern of thyroid gland enlargement and increased vascularity 4
Laboratory Tests
The following laboratory tests can be used to diagnose and monitor Graves' disease:
- TRAb test, which can help differentiate Graves' disease from other causes of hyperthyroidism 2
- fT3:fT4 ratio, which can be used to evaluate the severity of hyperthyroidism and predict disease prognosis 3
- Thyroid function tests, such as TSH, fT3, and fT4 levels, to monitor disease activity and response to treatment 4