Thyroid and Parathyroid Ultrasound
A thyroid and parathyroid ultrasound is a type of imaging test. It checks the thyroid gland and parathyroid glands. A thyroid ultrasound can help measure the size and shape of the thyroid gland. But it can't tell how well the thyroid gland is working. Ultrasound also may be used to check the four parathyroid glands that lie behind or next to the thyroid.
The thyroid gland makes a hormone called thyroxine. This hormone controls how fast the body converts food into energy (metabolism). Parathyroid hormone (PTH) is made by the parathyroid glands. It controls the amount of calcium and phosphorus in the blood.
During a thyroid and parathyroid ultrasound, a small handheld device called a transducer is passed back and forth over the neck. This makes a picture of the thyroid gland and parathyroid glands.
Why It Is Done
A thyroid and parathyroid ultrasound is done to:
- Check a lump (thyroid nodule) 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).
- Find out if the thyroid gland is too large. A thyroid ultrasound may also be used to keep track of the size of the thyroid gland during treatment for a thyroid problem.
- Guide the placement of the needle during a thyroid biopsy.
- Look for enlarged parathyroid glands caused by disease. Normal parathyroid glands are often hard to see on ultrasound. And they can't be felt during a physical exam. But abnormal parathyroid glands may be enlarged and easily seen by ultrasound.
How To Prepare
Talk to your doctor if you have any concerns about 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
This test 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 you may 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. You'll have a pillow under your shoulders. Gel will be spread on your neck. This helps the sound waves pass through better. (They do not pass easily through air.) A small water-filled bag or gelatin sponge might be placed over your throat. This also helps to conduct the sound waves. The transducer will be pressed against your neck (or against the water-filled bag or gelatin sponge, if used). Then it will be moved back and forth over your neck. A picture of your thyroid gland and the tissue around it can be seen on a video screen. You may be asked to turn your head away from the side being scanned so your jawbone is out of the way.
The test takes about 30 minutes. You may be asked to wait until the radiologist has reviewed the information. The radiologist may want to do more ultrasound views of your neck.
How It Feels
The gel may feel cold when it is put on your neck. Keeping your neck extended during the test may cause some discomfort. But you should not feel discomfort from the transducer or sound waves. You will be able to breathe and swallow normally during the test. You will not hear the sound waves.
There is very little chance of a problem from this test.
A thyroid ultrasound test does not use radiation. It is safe to use during pregnancy and will not harm your growing baby.
The thyroid gland and parathyroid glands are the right shape and are in the right place.
The glands are not too big or too small.
No growths or other problems are seen.
The parathyroid glands are too big.
What Affects the Test
You may not be able to have the test, or the results may not be helpful, if:
- You are not able to stay still during the test. Movement can affect the quality of the ultrasound picture.
- You have an open wound in the area that needs to be viewed.
What To Think About
- A radioactive thyroid scan and radioactive iodine uptake (RAIU) test are nuclear medicine tests. They use a radioactive substance to see how well the thyroid is working and to find thyroid problems. To learn more, see the topic Thyroid Scan.
- A thyroid ultrasound does not use a radioactive substance. It is easier to do. And it costs less than a radioactive thyroid scan or RAIU test. But a thyroid ultrasound does not show 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 find problems such as hyperthyroidism. A thyroid ultrasound can be used to find different types of thyroid problems, especially problems such as thyroid nodules.
- Thyroid nodules are common, especially in women and older people.
- Thyroid ultrasound can usually show the difference between a cyst, a solid nodule, or another type of mass that needs more 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 (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby.
Current as of: November 6, 2018
Author: Healthwise Staff
Medical Review: E. Gregory Thompson, MD - Internal Medicine
Kathleen Romito, MD - Family Medicine
Matthew I. Kim, MD - Endocrinology, Diabetes and Metabolism