Parathyroid Hormone (PTH) Blood Test

Parathyroid Hormone (PTH) Blood Test

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The PTH test is used to help identify hyperparathyroidism, to find the cause of abnormal calcium levels, or to check the status of chronic kidney disease. PTH controls calcium and phosphorus levels in the blood.

A parathyroid hormone (PTH) blood test measures the level of parathyroid hormone in the blood. This test is used to help identify hyperparathyroidism, to find the cause of abnormal calcium levels, or to check the status of chronic kidney disease. PTH controls calcium and phosphorus levels in the blood. PTH is made by the parathyroid glands, four pea-sized glandsbehind the thyroid gland. If the blood calcium level is too low, the parathyroid glands release more PTH. This causes the bones to release more calcium into the blood and reduces the amount of calcium released by the kidneys into the urine. Also, vitamin D is converted to a more active form, causing the intestines to absorb more calcium and phosphorus, which can decrease high PTH. If the calcium level is too high, the parathyroid glands release less PTH, and the whole process is reversed. PTH levels that are too high or too low can cause problems with the kidneys and bones and cause changes in calcium and vitamin D levels.

This hormone shouldn't be confused with the thyroid hormones because they serve different roles in the body.


What Is the Parathyroid Hormone?


The parathyroid hormone (PTH) is also known as parathyrin. It's responsible for influencing the calcium levels in the blood. For example, if the calcium levels drop, it can make the bones release more calcium in the bloodstream. At the same time, it can also facilitate the absorption of calcium into the bones and teeth when necessary.


What Are the Roles of PTH?


PTH serves several functions in the human body, mainly related to the absorption and release of calcium and phosphate. For example, let's take a look at how PTH affects the bones in your body.


1. The Rapid Absorption Phase


Once the parathyroid glands release a great quantity of PTH, the bone cells absorb calcium and phosphate in the bloodstream. The process starts within seconds from the moment of secretion of PTH. The bone cells (called osteocytes) fixate the calcium in the bones, making them stronger and less predisposed to fractures.


2. The Slow Release Phase


This phase consists of a release of calcium and phosphate in the bloodstream. PTH influence the bone cells to gradually break down the bone to release these minerals when necessary. The process takes days and even weeks, and it usually occurs when the calcium levelsin the blood drop to dangerous levels.


3. Effect on Kidneys


It is estimated that around 10% of all the calcium you get from food is lost through urine. When the blood calcium levels drop, the parathyroid glands release a lot of PTH to make the kidneys reabsorb some of the calcium in the urine. At the same time, PTH can also improve the release of phosphate in the urine, eliminating it from the body at a greater rate.


4. Improving Calcium Absorption in the Gut


Calcium gets absorbed better in the presence of vitamin D. When the calcium levels are low, the PTH transforms some 25 hydroxycholecalciferol into 1.25 dihydroxycholecalciferol. This hormone is a better version of vitamin D and will absorb more calcium in the stomach and intestines.


What Is A Parathyroid Hormone Test?


A PTH test is done to measure the levels of parathyroid hormone in the blood. To do that, doctors need a single blood sample drawn from the arm of a patient. You can order your PTH test online and obtain the results of the test in a few business days.


Depending on the results, your doctor might ask for more investigations or not. For example, if you have hypocalcemia, your doctor might consider supplementation with calcium. If your body also secretes low levels of PTH, the doctor might ask for a thorough investigation of your thyroid.


Make sure you stop supplementation with biotin (vitamin B7) for 72 hours before the test since this can alter the results.


What Are the Normal Levels of PTH In the Blood?


People who have normal levels of circulating PTH also enjoy stable calcium and phosphorus balance. They don't have kidney issues or problems with their bones. Here are the normal ranges of PTH in the body:


  • 50-330 ng/L for C-terminal and mid-molecule in adults
  • 51-217 ng/L for kids



Doctors measure other aspects related to the parathyroid hormone. For example, the ranges of PTH as an intact molecule are:


  • 0-65 ng/L for adults
  • 9-52 ng/L for kids



Anything that goes lower or higher than these reference values might be classified as hypoparathyroidism or hyperparathyroidism. A simple blood test will reveal if the parathyroid glands are functioning properly.


What are the symptoms of low PTH?


Certain symptoms will appear when the levels of PTH in your body get too low. For example:

  • Dry skin and dry hair
  • Headaches and memory problems
  • Cataracts and other eye conditions
  • Muscle spasms
  • Seizures
  • Abnormal heart rhythm
  • Poorly functioning kidneys
  • Teeth problems

It's important to note that these symptoms might be severe or mild for different people. That's why a PTH test is required to determine if the parathyroid glands are working fine. When the PTH levels get too low, your calcium levels will drop while the phosphorus ones will increase.


Various factors, such as an injury to the parathyroid glands due to surgery might cause low secretion of PTH. At the same time, some patients might have PTH in their blood, but an autoimmune diseaseprevents the patient's body from processing these hormones correctly.


What Are the Symptoms of High PTH?


It's also possible to have too much PTH in your blood. This is called hyperparathyroidism, and it can be split into two categories. It might be caused by enlarged parathyroid glands that secrete too much PTH. This can usually be fixed through surgery as the doctor removes the inflamed parathyroid gland.


Hyperparathyroidism can also be caused by very low calcium levels in the body. For example, if a different disease causes low calcium, the parathyroid gland might secrete too much PTH in an attempt to re-establish calcium balance in the body. The symptoms of hyperparathyroidism include:


  •  Abdominal pain
  •  Frequent and excessive urination
  •  Vomiting and nausea
  •  Bone pain
  •  Anxiety and depression
  •  Kidney problems
  •  Persistent weakness that doesn't go away after a good night's sleep


Get the PTH Test Today!

As you can see, the parathyroid glands are pulling the strings in the background to maintainstable calcium and phosphorus values in your body. If you want to enjoy having strong bones and vibrant health in general, you should do the PTH test as soon as possible. This test will reveal how healthy your parathyroid glands are and how much PTH is circulating in your body.


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  1. Go to the "Find a Location" page to find the closest lab location. No need to make an appointment since walk-ins are welcomed. Once you have identified your closest location, go to step 2.

  2. Go to "Choose a Test" and add your selection (s) in the shopping cart. If you prefer to save money on bundled tests, we have created "Lab Test Panels" that can help you decide what to order.

  3. If you have a discount coupon code, add it to your cart.

  4. A $8 lab processing fee will be added to your total.

  5. Pay using a credit card.

  6. You will receive an order confirmation and instructions email on how to download your lab request.

  7. Print lab request form that you downloaded.

  8. Take that form to the closest location. Get your blood drawn.

  9. You will receive an email when the results are ready for you to download.

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