Parathyroid Hormone (PTH)
- Also Known As:
- Intact PTH
Test Quick Guide
Parathyroid hormone (PTH) testing measures the level of parathyroid hormone in your blood. PTH is made by the parathyroid glands, which are two pea-sized glands located in the neck.
Parathyroid hormone controls the level of calcium in your blood and bones. It also helps regulate blood levels of phosphorus and vitamin D.
If you have too much or too little parathyroid hormone, it can cause abnormalities in blood calcium levels that may lead to serious health problems.
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 may use PTH testing to monitor whether a condition is improving, stable, or worsening in some patients with:
- Kidney disease
- Hyperparathyroidism, which is too much PTH in the blood
PTH levels may be tested during surgery for patients with 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?
Parathyroid hormone (PTH) is a chemical made by the parathyroid glands. These small, almond-shaped glands are located in the neck, near or behind the thyroid gland. PTH controls blood levels of calcium, phosphorus, and vitamin D.
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.
- PTH tells your digestive system to absorb more calcium from the food you eat.
- PTH 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 parathyroid hormone, 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 parathyroid hormone, calcium levels in the blood may be lower than normal. This condition is known as hypoparathyroidism.
When should I get parathyroid hormone testing?
The PTH test is often ordered when a blood test shows an abnormal level of calcium or when you have symptoms that suggest there is too much or too little calcium in the blood.
Abnormal calcium levels can be initially detected on a metabolic panel. A metabolic panel is a group of tests that are frequently performed to detect health problems before they cause symptoms. If a blood test shows an abnormal calcium level, a PTH test may be ordered to find out whether it is due to a problem with the parathyroid glands or something else.
PTH testing may also be ordered if you have symptoms that could be related to your blood calcium levels being too high or too low.
If your blood calcium levels are too high, you may experience symptoms that include:
- Increased thirst
- Frequent urination
- Mental changes, such as fatigue or confusion
- Bone pain
- Muscle twitching
- Muscle weakness
- Digestive upset, including nausea, appetite loss, and constipation
Symptoms of low blood calcium may include:
- Muscle cramps
- Dry skin
- Brittle fingernails
- Tingling in the lips, fingers, or feet
- Heart rhythm abnormalities
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.
Finding a Parathyroid Hormone Test
How to get tested
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.
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.
The costs of testing may include an office visit, a blood draw fee, and a laboratory fee for the analysis of your blood sample. These costs are usually covered by insurance when the test is ordered by your physician. You can check with your insurance provider to find out if you will be responsible for any deductibles or copays.
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Taking a Parathyroid HormoneTest
A parathyroid hormone test is performed on a sample of blood that is drawn during a visit to a doctor’s office, hospital, or similar medical setting.
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 sample of blood, 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 skin is pierced by the needle is cleaned with an antiseptic. A small amount of blood is withdrawn with a needle that is 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 the blood draw is complete, a band-aid or cotton swab is used to stop bleeding. You may be instructed to keep this in place for at least an hour.
Risks for the blood draw are low. In some settings, individuals may experience soreness, redness, or bruising in the area where the needle was used. Some individuals can feel nauseated at the sight of blood; while this is not unusual, relaxation techniques such as deep breathing can be helpful.
You are able to resume your normal activities, including driving, after the test is over. If you notice any pain, bleeding, or signs of infection after the test, you should call your doctor’s office.
Parathyroid HormoneTest Results
Receiving test results
PTH testing 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 10-65 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 the reference range, exceeds that range, or is below that range.
Higher than normal results of PTH can be an indication of a number of health issues including:
- Hyperparathyroidism, a disorder in which the parathyroid glands release too much PTH
- 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:
- Hypoparathyroidism, a condition in which the parathyroid glands release too little PTH
- 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.
Do I need follow-up tests?
Follow-up tests are common if you have an abnormal level of parathyroid hormone. Because many conditions can cause PTH to be high or low, there are numerous tests that can be used to identify the underlying cause and detect any health complications.
The choice of follow-up tests can depend on PTH test results, calcium levels, symptoms, and overall health. Possible tests include laboratory or imaging tests to assess the body’s nutrients, kidney function, and bone health.
Because follow-up testing is based on the doctor’s assessment, it is best to review the pros and cons of different test options with the doctor who ordered your PTH test.
Questions for your doctor about test results
The following questions may be helpful as you review your PTH test results with your doctor:
- Is my level of parathyroid hormone normal or abnormal?
- What do you think is the most likely cause of changes to my PTH levels?
- What other tests are necessary to confirm my diagnosis?
- Which is more appropriate for my situation: treatment or monitoring?
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