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How Is Hyperthyroidism Diagnosed?

Sunday, April 21, 2013 - 17:34
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Individuals with hyperthyroidism usually tell their doctors about symptoms such as rapid heart rate, intense fatigue, inability to tolerate a hot environment, and constant nervousness, jitteriness, or irritability. In addition, doctors look for physical signs such as weight loss, rapid heartbeat, slight tremors of the hands, or excessive sweating. The presence of such symptoms and signs strongly suggests the need for diagnostic testing for hyperthyroidism.

Hyperthyroidism is diagnosed from blood tests:

  • Abnormally high levels of T3 and T4. This indicates that hyperthyroidism is present.
  • An unusually low level of circulating thyroid stimulating hormone (TSH). This is normally due to an abnormality within the thyroid gland.

In some cases of hyperthyroidism, a special diagnostic scan of the thyroid gland using radioactive iodine called radioactive iodine uptake (RAIU) testing may be particularly useful. This test is often done on an outpatient basis in the nuclear medicine department of a hospital.

RAIU testing shows whether:

  • The entire thyroid gland is overactive, in which case, a large amount of radioactive iodine is "taken up" by the thyroid.
  • Only portions of the thyroid are overactive. Significant amounts of radioactive iodine are "taken up" by portions of the thyroid, not the entire gland.

Nice To Know:

Typically, Graves' disease produces increased iodine uptake throughout the thyroid gland.Nodular thyroid disease produces a scan that shows patches of increased iodine uptake surrounded by areas with normal uptake.

How Is Graves' Disease Diagnosed?

Most people with hyperthyroidism, or about 95 percent, are eventually diagnosed with Graves' disease.

The diagnosis is confirmed through laboratory testing.

In people with Graves' disease, blood tests usually demonstrate:

  • Increased levels of T3
  • Increased levels of T4
  • Low levels of TSH
  • Presence of thyroid stimulating antibodies

A radioactive scan, such as RAIU testing, is usually not necessary to confirm the diagnosis of Graves' disease. If a scan is performed, it typically shows increased uptake of radioactive iodine throughout an enlarged thyroid gland. Areas of iodine uptake represent those areas in the gland producing thyroid hormone.

How Is Nodular Thyroid Disease Diagnosed?

When a physical exam is performed, the thyroid is usually larger than normal; however, there is usually no pain associated with an enlarged thyroid. As untreated disease progresses, individual lumps or nodules may be felt with the fingertips.

RAIU testing may be used to diagnose nodular thyroid disease. In individuals with this form of hyperthyroidism, this test shows clusters or nodules of abnormal thyroid cells among areas of normal cells. After this test, doctors see "spots" of overactivity on radioactive iodine uptake scanning film.


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