Generally speaking, a patient’s hyperthyroidism diagnosis will be the result of a TSH blood test. Oftentimes, a correct diagnosis can take years as symptoms are so varied and may wax and wane.

Once a diagnosis of hyperthyroidism has been made, the next step would be to find out what is the cause of the hyperthyroidism.

The definitive test for diagnosing Graves’ disease is a blood test called Thyroid Stimulating Immunoglobulin (TSI). TSI are the autoantibodies responsible for overstimulating the thyroid gland causing Graves’ disease.

Other diagnostic tests, which do not definitively diagnose Graves’ but are often done during a diagnostic workup are:

Thyroid Uptake and Scan

Generally a two-day test done with a tracer dose of radioactive iodine (RAI), most often I-123, which is either swallowed or injected into the patient. The patient is then scanned by a machine at either the 4-hour or 6-hour mark and again at the 24-hour mark after ingesting the radioactive iodine.

Thyroid Ultrasound

A test which uses sound waves to visualize the thyroid gland. This test can be used to see the consistency, shape and size of any thyroid nodules. Ultrasound is also used to measure the size of the thyroid gland itself.

Thyroid Biopsy (also called an FNA – Fine Needle Aspiration)

This test extracts a piece, or pieces, of thyroid gland tissue to be examined under microscope for abnormal cells. It is used in diagnosing thyroid cancer from other benign thyroid conditions.

Lab Blood Tests

From The Merck Manual of Medical Information – Second Home Edition, p.951, edited by Mark H. Beers. Copyright 2003 by Merck & Co., Inc., Whitehouse Station, NJ. Available at: Accessed 3/27/07.

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