About the Test
Purpose of the test
PTH testing may be ordered to diagnose the underlying cause if you have signs of a health problem such as:
- Too much or too little calcium in the bloodstream
- Low levels of phosphorus in the blood
- Severe osteoporosis
Doctors also use PTH testing to monitor whether a condition is improving, stable, or worsening in some patients with kidney disease or hyperparathyroidism, which is too much PTH in the blood.
PTH levels may be tested during surgery if you have overactive parathyroid glands. The test results enable the surgical team to confirm that the overactive tissues have been successfully removed.
What does the test measure?
A PTH measures a protein hormone released by the parathyroid gland into the bloodstream. It can also show whether there is too little or too much calcium in the blood, indicating a thyroid issue.
When should I get this test?
A PTH test may be ordered to find out whether it is due to a problem with the parathyroid glands or something else. If your blood calcium levels are too high, you may experience symptoms that include increased thirst, frequent urination, fatigue, confusion, bone pain, muscle twitching or weakness, upset stomach, appetite loss, and constipation.
On the other hand, if your blood calcium levels are too low, you might experience symptoms like muscle cramps, dry skin, brittle fingernails, tingling in the lips, fingers, or feet, seizures, or heart rhythm abnormalities.
Also, ongoing PTH testing may be used in some people who have previously been diagnosed with hyperparathyroidism. PTH testing is also ordered to monitor patients with chronic kidney disease.
The parathyroid glands produce more PTH when calcium levels in the body are low. PTH sends chemical messages to other organs to balance blood calcium levels. For example, PTH:
- Signals your bones to release some of their calcium into the blood.
- Tells your digestive system to absorb more calcium from the food you eat.
- Instructs your kidneys to retain calcium in the body rather than flushing it out in urine.
After its release from the parathyroid glands, PTH is active in the body for only a few minutes. When blood calcium levels rise, the parathyroid glands stop releasing PTH.
In some patients, the parathyroid glands release too much PTH, a condition known as hyperparathyroidism. When too much PTH is released into the blood, calcium levels in the bloodstream will be elevated.
If the parathyroid glands release too little PTH, calcium levels in the blood may be lower than normal. This condition is known as hypoparathyroidism.
Finding a PTH Test
To take a PTH test, you’ll need to get blood drawn at a clinic or doctor’s office. However, there are thyroid and hormone tests available online or over the counter that you can take without getting a physician’s referral.
How can I get a PTH test?
Typically, PTH testing is ordered by a doctor, and a blood sample for analysis will be drawn in a medical setting like a doctor’s office, lab, or clinic.
Can I take the test at home?
Test kits for home testing of PTH are not commercially available at this time, but you can find at-home hormone and at-home thyroid test kits online.
How much does the test cost?
The cost of PTH testing depends on where the test is performed, whether other tests are done at the same time, and whether or not you have medical insurance.
Testing costs may include an office visit, a blood draw fee, and a laboratory fee to analyze your blood sample. These costs are usually covered by insurance when your physician orders the test. You can check with your insurance provider to determine if you will be responsible for any deductibles or copays.
Taking a PTH Test
A PTH test is performed on a blood sample that is drawn during a visit to a doctor’s office, hospital, or similar medical setting. However, you can order thyroid and hormone tests to take at home.
Before the test
Most of the time, no special preparations are required for a PTH test. You can check with your doctor about whether you need to avoid eating or drinking before the test. They can also tell you whether you should schedule your blood draw for a particular time of day.
During the test
During a PTH blood test, a nurse or other health care provider takes a blood sample, usually from a vein in your arm. An elastic band is tied around your upper arm to make it easier to locate a vein. The site where the needle pierces the skin is cleaned with an antiseptic.
A small amount of blood is withdrawn with a needle attached to a collection tube. You may feel a brief sting when the needle punctures the skin. It usually takes less than a minute to obtain a blood sample.
After the test
After a PTH blood test, you might experience some bruising or soreness where the blood sample was drawn. Since you must fast before this test, it’s a good idea to bring a snack or drink with you in case you feel lightheaded. Otherwise, there are no restrictions following a PTH test, and you can resume your typical everyday activities.
PTH Test Results
Receiving test results
PTH results are usually available within a few days. Your doctor or someone on the doctor’s staff may contact you to share results over the phone or to schedule an appointment so you can discuss them with the doctor. You may also be able to access your PTH test results using an online patient portal.
Interpreting test results
What is considered a normal PTH level, known as the reference range, can vary slightly depending upon the laboratory that performs the test. The American Board of Internal Medicine considers PTH levels between 10 to 65 picograms per milliliter (pg/mL) to be within normal limits.
You can check your test report or ask your doctor what reference range was used to interpret your PTH results. The test report should indicate whether your test result is within, exceeds, or is below that reference range.
Higher than normal results of PTH can be an indication of many health issues including:
- Vitamin D disorders
- Insufficient calcium intake, poor calcium absorption, or excess calcium loss in urine
- Long term kidney disease that affects minerals in the blood like phosphorus
- Tumors of the parathyroid gland
- Pseudohypoparathyroidism, a condition in which the body fails to respond to PTH
A lower than normal level of PTH in the blood may be due to:
- Injury to the parathyroid glands from surgery, radiation, or other causes
- Autoimmune disorders that damage the parathyroid glands
- Cancers that have spread to the bone
- Long-term excess calcium intake from supplements or antacids
- Too much vitamin D intake
- Low blood magnesium
- Tumors in the parathyroid glands
Sometimes PTH levels do not closely correspond to calcium levels in the blood. In some cases, a PTH level may be in the normal range when calcium levels are abnormal. The doctor may classify this type of PTH level as “inappropriate.”
Because abnormal PTH levels can be associated with a wide range of health conditions, it is important to discuss the significance of your test results with your doctor. Follow-up tests are common if you have an abnormal level of PTH.