The Anatomy of the Parathyroid Gland

Four small glands in the neck regulate calcium and phosphorus

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The parathyroid is a set of four glands located in your neck, just behind the thyroid gland. Parathyroid glands are responsible for regulating the calcium and phosphorus levels in your body.

In order to manage the amount of these minerals, the parathyroid uses the parathyroid hormone (PTH). If there is an imbalance of calcium in the bloodstream, the parathyroid will either stop or increase the parathyroid hormone production.

Primarily black and white photo of the human neck. There are four red and yellow spots near the center of the neck indicating the location of the parathyroid.
Kateryna Kon, Getty Images

Anatomy

The parathyroid consists of four individual glands in the neck. These glands vary in size from one person to another. However, a healthy parathyroid gland will be somewhere between the size of a grain of rice and a pea. These four glands are typically attached to the back of the thyroid at the top and bottom of each lobe.

If you feel your neck just below the Adam's apple, there's a soft spot. This area is about where your thyroid sits. You will most likely find the parathyroid glands on the backside of the thyroid.

Occasionally, but not often, the parathyroid glands can be found elsewhere in the neck. They can be found anywhere between the neck and the chest. If you've had your thyroid removed, the parathyroid will be attached to another spot in your neck.

Because the parathyroid is attached to the thyroid and shares a similar name, many people mistakenly believe they are similar. However. the thyroid and parathyroid are two different organs providing completely separate functions.

Function

The parathyroid plays a vital role in regulating and balancing both calcium and phosphorus in your bones and blood.

The parathyroid works by monitoring and controlling calcium levels in the body. If the parathyroid detects too much calcium, it will stop producing the hormone. When the calcium levels get too low, the parathyroid will release PTH.

Parathyroid hormone release triggers the body to release some of the calcium our body has stored in our bones. The bones will release this calcium into the bloodstream. The blood carries the calcium through our body and releases it into the digestive system, where it will be absorbed and put to work.

On the flip side, if the body has too much calcium, the parathyroid will slow down or stop producing PTH until the levels return to normal.

Associated Conditions

The most common, serious, and widely known condition of the parathyroid is hyperparathyroidism sometimes known as parathyroid disease. This condition occurs when the parathyroid cannot properly regulate calcium and is producing too much PTH.

Hyperparathyroidism creates excess calcium in the bloodstream, which negatively affects multiple organs and can potentially lead to organ failure. One dangerous consequence is an abnormal heart rhythm; the condition can also cause kidney stones or fragile bones that can break easily. Hyperparathyroidism is considered more dangerous than parathyroid cancer.

The opposite of hyperparathyroidism is hypoparathyroidism, which is less common. Hypoparathyroidism occurs when the parathyroid isn't acting to maintain levels of blood calcium. This affects the body's muscles and nerves, among other things.

Hypoparathyroidism can occur if the parathyroid glands are malfunctioning or if the kidneys and bones are not correctly registering the presence of PTH. Often it occurs following injury to the parathyroid during a neck procedure, such as thyroid surgery, or after radiation treatment for head or neck cancer. But it can also be due to an autoimmune process or other causes.

While rare, it is possible to have parathyroid cancer. It's important to know, parathyroid cancer has an excellent recovery rate. In fact, up to 85% of people with parathyroid cancer will live at least five years after their diagnosis.

Tests

While there are a few tests specific to the parathyroid, your doctor may require more tests than listed here. While it's important to know the parathyroid is not working correctly, it's essential to understand why.

Lab Tests

When determining if someone has a parathyroid disorder, a healthcare provider will request a series of lab tests. Most often, they will be looking for the presence of PTH and calcium levels in your blood.

Sometimes your doctor will also check for vitamin D, albumin, phosphate, and magnesium. All of these lab tests will give your healthcare provider a good idea about how calcium is moving through your body. 

Occasionally, your provider may request a urine test as well. If any of these levels are out of range, in either the blood or urine, it can indicate a problem needing treatment. 

Ultrasound of the Parathyroid

An ultrasound is one of the first tests your primary care provider or endocrinologist will request when identifying a parathyroid problem. 

An ultrasound tech will place a gel on your neck and use a wand to gather images of your thyroid and parathyroid. They will measure the glands and look to see if there's blood flow in the area. This test can help identify the location and size of a tumor on the parathyroid gland.

Sestamibi Scan

A sestamibi scan is used to find an overactive parathyroid gland. This scan creates pictures of inside structures, including cancer cells. This scan helps diagnose and monitor parathyroid cancer.

During this test, you are given a radioactive chemical. The nurse or radiology technician will give you this chemical either as something you can swallow or through an injection. The parathyroid absorbs the chemical. Then, when the radiology tech is taking the images, the cells and organs that absorbed the chemical appear differently than other cells or organs. 

Having images showing specific accumulation of parathyroid cells allows doctors to see where the cancer cells are clustering. This information not only shows if the cancer is spreading, but it can also identify which of the four parathyroid glands are affected by cancer.

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