Parathyroid Hormone - What is it?

PTH is made by four tiny parathyroid glands in your neck. These glands control calcium levels in your blood. When calcium levels are too low, the glands release PTH to bring the calcium levels back up into a normal range. When your calcium levels rise, the glands stop releasing PTH.

Measuring PTH can help explain the reason for abnormal calcium levels.

In preparing for the testing, you need fasting for 10 hours.

Three forms of PTH are measured in this test. The exact normal ranges vary based on the lab doing the testing. The results are described in picograms per milliliter (pg/mL). Discuss the results with your health care provider so that you understand what these numbers mean. The three forms of PTH and some fairly typical normal ranges are:

  • N-terminal: 8 to 24 pg/mL
  • C-terminal: 50 to 330 pg/mL
  • Intact molecule: 10 to 65 pg/mL

High PTH levels could be caused by overactive parathyroid glands. This is called hyperparathyroidism. However, there are other potential causes of high PTH levels, such as:

  • Inherited low vitamin D level
  • Spinal cord injury
  • Low calcium unrelated to parathyroid glands
  • Kidneys that don’t respond normally to PTH

Low PTH levels could be related to underactive parathyroid glands (hypoparathyroidism). Other causes could include:

  • Radiation
  • Iron overload
  • Surgery for thyroid disease
* The Content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.