A thyroid and parathyroid ultrasound is an imaging test to check the thyroid gland and parathyroid glands. A thyroid ultrasound can help measure the size and shape of the thyroid gland, but it cannot tell how well the thyroid gland is working. Ultrasound also may be used to check the four parathyroid glands that lie behind to the thyroid. See an illustration of the thyroid gland and parathyroid glands.

The thyroid gland makes a hormone called thyroxine that controls how fast the body converts food into energy (metabolism). Parathyroid hormone (PTH) is made by the parathyroid glands and controls the amount of calcium and phosphorus 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 form a picture of the thyroid gland and parathyroid glands.

Why It Is Done

A thyroid and parathyroid ultrasound is done to:

• Check lumps (nodules) in the thyroid gland. A thyroid ultrasound can usually show the difference between a solid thyroid gland nodule and a simple fluid-filled sac (cyst). See an illustration of a thyroid nodule.
• Find out whether the thyroid gland is enlarged. A thyroid ultrasound may also be used to keep track of the size of the thyroid gland during treatment for a thyroid problem.
• Look for 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 easily seen by ultrasound.
• Guide the placement of the needle during a thyroid biopsy.

How To Prepare

No special preparation is required before having this test. You will need to remove jewelry from your head or neck before the test.

Talk to your health professional about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results may mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).

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 your head or 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 the tissue around it 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.