Parathyroid Hormone Test (PTH) -Why am I having this test?

Parathyroid Hormone Test may be used to evaluate the function of your parathyroid glands and to check for or monitor conditions that affect the calcium levels in your body.

The parathyroid glands are four tiny glands that surround the larger thyroid gland in your neck. When your blood calcium levels are low, your parathyroid glands release PTH into the blood. This causes several changes in your body that result in an increase in your blood calcium level. When blood calcium levels are normal or too high, blood PTH levels decrease.

Your health care provider may want you to have this test if you have:

• Signs of higher-than-normal blood calcium levels (hypercalcemia).
• Signs of lower-than-normal blood calcium levels (hypocalcemia).
• A kidney infection.
• Kidney disease.
• Certain cancer cells that secrete PTH.

What is being tested?

This test measures the amount of PTH in your blood.

What kind of sample is taken?

A blood sample is required for this test. It is usually collected by inserting a needle into a blood vessel or by sticking a finger with a small needle.

How do I prepare for this test?

Do not eat or drink anything after midnight on the night before the test or as told by your health care provider.

How are the results reported?

Your test results will be reported as values that indicate the amount of PTH in your blood. Your health care provider will compare your results to normal ranges that were established after testing a large group of people (reference ranges). The results may include amounts for whole PTH and its fragments (PTH N-terminal and PTH C-terminal). Reference ranges may vary among labs and hospitals. For this test, common reference ranges are:

• PTH intact (whole): 10–65 pg/mL or 10–65 ng/L (SI units).
• PTH N-terminal: 8–24 pg/mL or 8–24 ng/L (SI units).
• PTH C-terminal: 50–330 pg/mL or 50–330 ng/L (SI units).

What do the results mean?

Test results that are higher than the reference range may mean that you have:

• Overactive parathyroid glands (hyperparathyroidism).
• A non-parathyroid PTH-producing tumor.
• A kidney defect that is present at birth (congenital).
• Hypocalcemia.
• Long-term (chronic) kidney failure.
• Malabsorption syndrome. This means that your body does not properly absorb nutrients such as calcium from the intestinal tract.
• Vitamin D deficiency. Adequate vitamin D levels are required for calcium to be absorbed from the intestinal tract. Vitamin D deficiency can lead to low levels of calcium in the blood.

Test results that are lower than the reference range may indicate any of the following:

• Underactive parathyroid glands (hypoparathyroidism).
• Hypercalcemia.
• Bone tumor.
• A disease that causes inflammation in your organs and other areas of your body (sarcoidosis).
• Vitamin D intoxication.
• Milk-alkali syndrome.
• An immune system disorder (DiGeorge syndrome).

Talk with your health care provider about what your results mean.

Questions to ask your health care provider

Ask your health care provider, or the department that is doing the test:

• When will my results be ready?
• How will I get my results?
• What are my treatment options?
• What other tests do I need?
• What are my next steps?

Summary

• The parathyroid hormone (PTH) test may be used to evaluate the function of your parathyroid glands and to check for or monitor conditions that affect the calcium levels in your body.
• The parathyroid glands are four tiny glands that surround the larger thyroid gland in your neck.
• When your blood calcium levels are low, your parathyroid glands release PTH into the blood.
• Talk with your health care provider about what your results mean.