THYROID AND PARATHYROID ULTRASOUND

A thyroid and parathyroid ultrasound is an imaging test to evaluate the thyroid gland and parathyroid glands. A thyroid ultrasound can help determine the size and shape of the thyroid gland, but it cannot determine the function of the thyroid. Ultrasound also may be used to evaluate the four parathyroid glands that lie within or next to the thyroid.

The thyroid gland produces a hormone called thyroxine that controls how fast the body converts food into energy (metabolism). Parathyroid hormone, or PTH, is produced by the parathyroid glands and regulates calcium and phosphorus levels in the blood.

During a thyroid and parathyroid ultrasound, a small handheld instrument called a transducer is passed back and forth over the neck to produce a picture of the thyroid gland and parathyroid glands.

Why It Is Done

A thyroid and parathyroid ultrasound is done to:

• Evaluate lumps that can be felt on the thyroid gland. It also can be done to evaluate lumps found during a thyroid scan. A thyroid ultrasound can usually distinguish between a solid thyroid gland tumor and a simple fluid-filled sac (cyst).
• Determine whether the thyroid gland is enlarged. A thyroid ultrasound may also be used to monitor the size of the thyroid gland during treatment for a thyroid problem.
• Detect enlarged parathyroid glands caused by disease. Normal parathyroid glands are often difficult to see on ultrasound and cannot be felt during physical examination. However, abnormal parathyroid glands may be enlarged and detectable by ultrasound.
• Guide the placement of the needle during a thyroid biopsy.

How To Prepare

No special preparation is required before having this test. Avoid wearing jewelry on your head and around your neck because you will need to remove it before the test.

How It Is Done

A thyroid and parathyroid ultrasound is usually done by a radiologist or by an ultrasound technologist. It is done in an ultrasound room in a doctor's office or hospital.

You may be asked to undress above the waist and drape a paper or cloth covering around your shoulders. Remove all jewelry from around your neck.

You will lie on your back on a high table with your neck stretched out and a pillow under your shoulders. Gel will be spread on your neck to improve the passage of the sound waves (they do not pass easily through air). Sometimes a small water-filled bag or gelatin sponge is placed over your throat to help conduct the sound waves. The transducer will be pressed against your neck (or against the water-filled bag or gelatin sponge, if used), then moved back and forth over your neck. A picture of your thyroid gland and surrounding tissue can be seen on a video monitor. You may be asked to turn your head away from the side being scanned so the jawbone is out of the way.

A thyroid ultrasound test takes about 30 minutes. You may be asked to wait until the radiologist has reviewed the information. The radiologist may want to do additional ultrasound views of your neck.

How It Feels

The gel may feel cold when it is applied to your neck. Keeping your neck extended during the test may become mildly uncomfortable, but you should feel no discomfort from the transducer or sound waves. You will be able to breathe and swallow normally during the test, and you will not hear the sound waves.

Risks

There are no known risks associated with a thyroid or parathyroid ultrasound test.

A thyroid ultrasound test does not use radiation, so it is safe to use during pregnancy and poses no harm to your developing baby (fetus).

Results

A thyroid and parathyroid ultrasound is an imaging test to evaluate the thyroid gland and parathyroid glands. The results of a thyroid or parathyroid ultrasound test are usually available within several days.

What Affects the Test

Factors that can interfere with your test and the accuracy of the results include:

• Inability to hold still during the procedure. Movement can interfere with the quality of the ultrasound picture.
• Having an open wound in the area that needs to be viewed.