Thyroid and Parathyroid Ultrasound

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.

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.

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?).

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.

The gel may feel cold when it is applied to your neck. Keeping your neck extended during the test may be uncomfortable, but you should not feel 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.

There is very little chance of a problem from a thyroid or parathyroid ultrasound test.

A thyroid ultrasound test does not use radiation, so it is safe to use during pregnancy and will not harm your growing baby.

A thyroid and parathyroid ultrasound is an imaging test to check the thyroid gland and parathyroid glands. The results of a thyroid or parathyroid ultrasound test are usually available within 2 to 3 days.

Reasons you may not be able to have the test or why the results may not be helpful include:

• Not being able 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.

• A radioactive thyroid scan and radioactive iodine uptake (RAIU) test are nuclear medicine tests that use a radioactive substance to see how well the thyroid is working and identify thyroid problems. For more information, see the medical test Thyroid Scan.
• A thyroid ultrasound does not use a radioactive substance; it is easier to perform and is less expensive than a radioactive thyroid scan or RAIU test. However, a thyroid ultrasound does not provide information about how well the thyroid gland is working.
• A thyroid ultrasound may be done at the same time as an RAIU test. RAIU testing is used more often than a thyroid ultrasound to identify problems, such as hyperthyroidism or hypothyroidism. A thyroid ultrasound can be used to identify different types of thyroid problems, especially problems such as thyroid nodules.
• Thyroid nodules are common, especially in women and older people. Since only a small number of thyroid nodules contain cancer cells, most doctors initially choose to watch the nodule closely instead of using surgery to remove it.
• Thyroid ultrasound can usually show the difference between a cyst, a solid nodule, or another type of mass that needs further testing. A fluid-filled sac that is smooth and round and that does not have any particles floating in it is likely to be a simple cyst. A lump that does not have any fluid or that has fluid with floating particles needs to be checked more closely. If a solid nodule is found, a thyroid biopsy may be needed.

Other Works Consulted

• Pagana KD, Pagana TJ (2006). Mosby’s Manual of Diagnostic and Laboratory Tests, 3rd ed. St. Louis: Mosby.