Hyperthyroidism diagnosis

If you experience any of the signs or symptoms of hyperthyroidism, see your healthcare provider.

In order to diagnose¹⁸ hyperthyroidism, your healthcare provider will usually evaluate your medical history, perform a physical assessment, and order one or more lab tests. Testing used to diagnose hyperthyroidism may include:

• Medical history and physical exam: During the exam, your provider may ask you to extend your arms so he or she can look for a slight tremor in your fingers. He or she will check for a number of signs and symptoms, including overactive reflexes, eye changes, and warm, moist skin. Your provider will also examine your thyroid as you swallow to see if it's enlarged, bumpy, or tender and will check your pulse to see if it's rapid or irregular.
• Blood tests: Blood tests that measure thyroxine and thyroid-stimulating hormone (TSH) can be used to confirm a diagnosis of hyperthyroidism. High levels of thyroxine and low amounts of TSH indicate an overactive thyroid. The amount of TSH you produce is important because it's the hormone that signals your thyroid to produce more thyroxine.

These tests are especially useful for older adults, who may not show typical or obvious symptoms of hyperthyroidism.

Thyroid blood tests may produce false results if you're taking biotin, a B vitamin supplement that may also be found in multivitamins. Let your healthcare provider know if you are taking supplements that include biotin.

If your blood tests indicate hyperthyroidism, your provider may recommend one of the following tests to help determine the reason for your thyroid’s overactivity:

• Radioiodine uptake test: This test involves taking a small oral dose of radioactive iodine (radioiodine) to see how much of it your thyroid collects. You'll be checked after 4, 6, or 24 hours to see how much of the iodine your thyroid has absorbed.

A high uptake of radioiodine indicates that your thyroid is producing too much thyroxine. The most likely cause of this is either Graves' disease or hyperfunctioning thyroid nodules (cysts that are usually benign, or non-cancerous).

If you have hyperthyroidism and a low radioiodine uptake, the thyroxine stored in your thyroid is probably leaking into the bloodstream, indicating thyroiditis.

• Thyroid scan: This test is also used to determine how much iodine collects in your thyroid. During this test, a radioactive isotope is injected into a vein in the crook of your elbow or your hand. You then lie on a table with your head stretched backward while a special camera produces an image of your thyroid on a computer screen.

• Thyroid ultrasound: This test uses high-frequency sound waves to produce images of the thyroid. Ultrasound may be better suited to accurately detect thyroid nodules than other tests. Thyroid ultrasound does not expose you to harmful radiation, which can be a risk factor for thyroid diseases.