What are the Parathyroid Glands?
- Most people have four small parathyroid glands located behind the thyroid gland in the neck
- These glands regulate calcium levels in your body
- Sometimes one or more of these glands becomes overactive (hyperparathyroidism), producing too much parathyroid hormone
- This excess hormone causes high calcium levels in your blood, which can lead to various health problems
Why Might I Need a Parathyroid Scan?
Your doctor may recommend this scan if:
- You’ve been diagnosed with hyperparathyroidism (based on blood tests showing high calcium and parathyroid hormone levels)
- You have symptoms of high calcium levels, such as bone pain, kidney stones, fatigue, or digestive problems
- Surgery is being considered to remove the overactive parathyroid gland(s)
- The surgeon needs to know exactly which gland(s) to remove
How Does a Parathyroid Scan Work?
This scan uses a substance called Sestamibi that is labeled with a small amount of radioactive material (Tc-99m pertechnetate). The test works because:
- Sestamibi concentrates in overactive parathyroid tissue (adenomas)
- A special camera (gamma camera) detects the radiation emitted by the Tc-99m Sestamibi
- The overactive parathyroid gland(s) appear as “hot spots” on the images
- The concentration of Sestamibi increases over time in parathyroid adenomas, while decreasing in normal tissue
Sometimes, the thyroid gland also takes up the Sestamibi, making it difficult to distinguish parathyroid abnormalities. In these cases, a second radioactive tracer (pertechnetate) that only accumulates in thyroid tissue may be used. By comparing or subtracting these two sets of images, we can more clearly identify parathyroid abnormalities.
What to Expect During the Procedure
Before the Scan
- No special preparation is typically required
- You can eat and drink normally before the test
- Wear comfortable clothing without metal objects in the neck area
- Inform your doctor if you are pregnant or breastfeeding
During the Scan
- You’ll receive an injection of the Sestamibi tracer into a vein in your arm
- This feels similar to having blood drawn
- The tracer will not make you feel different
- Multiple imaging sessions will be performed:
- First images taken about 15 minutes after injection
- Additional images taken at 1 hour, 2 hours, and 3 hours after injection
- Each imaging session takes about 15-20 minutes
- You’ll need to lie still with your neck in a slightly extended position
- A CT scan will be also be acquired to better localise the hyperfunctioning parathyroid tissue anatomically
- For some patients, at the 3-hour mark:
- A second tracer (pertechnetate) may be injected
- Additional images will be taken about 20 minutes after this injection
- Between imaging sessions, you may be able to wait in a designated area or leave the department temporarily
After the Scan
- You can resume all normal activities immediately
- Drink plenty of fluids to help flush the tracer from your body
- The small amount of radiation will naturally leave your body within a day
- A nuclear medicine specialist will analyze your images and send a report to your doctor
- Your doctor will discuss the results with you at your next appointment
Are There Any Risks?
The parathyroid scan uses a very small amount of radiation. The benefits of identifying the overactive parathyroid gland(s) far outweigh any potential risks from this minimal radiation exposure.
If you have any questions or concerns about your parathyroid scan, please discuss them with your healthcare provider.
