A parathyroid hormone test measures levels of parathyroid hormone (PTH) in your body. This hormone is produced by small glands in your neck and regulates the level of calcium in your blood.
A parathyroid test measures the amount of PTH in your blood. An important job of PTH is to regulate the amount of calcium in your blood, which is essential for your nerves, muscles, and heart to function properly.
Your doctor may order a PTH test if you have certain symptoms or conditions, such as osteoporosis, chronic kidney disease, or seizures.
Read on for more information about PTH testing, why you may need it, and how your doctor may use it for your care.
The parathyroid glands are four glands located in your neck near your thyroid gland. They produce a hormone called PTH that helps regulate calcium, vitamin D, and phosphorus levels in your blood and bones.
Calcium imbalances in the blood may be a sign of parathyroid gland or PTH issues. Calcium levels in the blood signal the parathyroid glands to release or suppress PTH.
Healthy calcium levels are essential for your body to function properly. Your doctor may need to measure your PTH if your blood calcium test is abnormal or if they need to figure out the cause of too much or too little calcium in your blood.
Too much calcium could be a sign of hyperparathyroidism, a condition caused by overactive parathyroid glands that produce too much PTH. Excess calcium in the blood can lead to kidney stones, irregular heartbeats, and brain abnormalities.
Too little calcium could be a sign of hypoparathyroidism. This is a condition caused by underactive parathyroid glands that aren’t producing enough PTH. Not enough calcium in the blood could lead to:
- osteomalacia (weakened bones)
- muscle spasms
- heart rhythm disturbances
- tetany (overstimulated nerves)
Your doctor may also order this test to:
- check parathyroid function
- distinguish between parathyroid-related and nonparathyroid-related disorders
- monitor the effectiveness of treatment in parathyroid-related issues
- determine the cause of low phosphorus levels in your blood
- determine why severe osteoporosis isn’t responding to treatment
- monitor chronic conditions, such as kidney disease
The risks of a PTH test are mild and are generally the same as any other blood test. They include:
A PHT test can identify problems with PTH levels in the body.
This test also helps healthcare professionals determine if you need other testing, diagnose conditions, and choose the best treatment options for you.
You’ll need to get your blood drawn for a PTH test.
Before having this test, tell your doctor if you have hemophilia, a history of fainting, or any other condition.
Venipuncture is the process of taking a blood sample for testing. A healthcare professional usually draws blood from a vein in the inner elbow or back of the hand. Here are the steps for a blood draw:
- Your healthcare professional will sterilize the area with an antiseptic. Then, they’ll wrap a plastic band around your arm to apply pressure and help your veins swell with blood.
- After your veins swell, your healthcare professional will insert a sterile needle directly into the vein and collect the blood in an attached vial.
- When there is enough blood for the sample, they’ll untie the elastic band and remove the needle from your vein. They may also clean and bandage the area where they inserted the needle.
Following the test, you may experience some pain from the needle prick, and you may bleed where the needle broke the skin. For most people, this bleeding is minimal and won’t cause any issues.
Specific numeric results from PTH testing will vary slightly from lab to lab and depend on the system they use. Your doctor or healthcare professional can help you understand what your results mean.
They may use these results to assist with determining a diagnosis, treatment plan, or both.
Here is a closer look at PTH test results:
Normal results
Your doctor will interpret your PTH test results. Labs may report results in slightly different ranges, so there is a range of what’s considered normal for this test. Your doctor will know the normal range for the lab you’re using.
It’s important to talk with your healthcare professional about what your results mean. Be sure to use the same lab for follow-up testing so they can accurately compare your results.
PTH test results may be only one of several lab tests performed, so a normal PTH test may not tell your doctor everything they need to know about your symptoms or condition.
For example, you may have a normal PTH test and high blood calcium levels. If PTH levels are normal and calcium levels are low or high, the issue may not be your parathyroid glands. This information helps your doctor determine why you may have high calcium levels.
Low PTH levels
If PTH levels are low, you may have a condition causing low calcium levels. Or you may have an issue with your parathyroid glands.
Low PTH levels could also indicate:
- a low level of calcium in your blood
- too little calcium in your diet
- difficulty absorbing enough calcium
- losing calcium through urination
- hypoparathyroidism
- an autoimmune disorder
- cancer originating from another part of the body has spread to the bones
- ingestion of excess calcium over a long period of time (from milk or certain antacids)
- low levels of magnesium in the blood
- radiation exposure to the parathyroid glands
- vitamin D intoxication
- sarcoidosis (a disease that causes tissue inflammation)
High PTH levels
If PTH levels are high, you could have hyperparathyroidism. Hyperparathyroidism is commonly due to a benign parathyroid tumor.
High PTH levels could also indicate:
- vitamin D disorders
- difficulty breaking down, absorbing, or using vitamin D
- conditions that cause increased phosphorus levels, like chronic kidney disease
- pseudohypoparathyroidism (your body isn’t responding to PTH)
- swelling or tumors in the parathyroid glands
If your PTH levels, calcium levels, or both are too high or too low, your doctor may want to perform additional testing to help make an accurate diagnosis and create a treatment plan.
Parathyroid hormone testing measures the level of PTH in your body. Your PTH levels help doctors evaluate your health and determine if your parathyroid glands are functioning properly.
PTH helps regulate calcium levels in the body, and adequate calcium levels are essential for the proper functioning of the heart, muscles, and nerves.
If these glands aren’t functioning properly, it may cause other health conditions, such as osteoporosis, chronic kidney disease, or seizures.
Following a PTH test, you’ll meet with your doctor or healthcare professional to discuss the results. Depending on your results, you may need additional tests, you may receive a diagnosis, or you may need to modify your existing treatment plan.