PTH Test: Diagnosing Parathyroid and Calcium Disorders

What Is the PTH Test?

The PTH test, short for parathyroid hormone test, is a blood test that measures the level of parathyroid hormone (PTH) in your body. PTH is produced by four tiny parathyroid glands in your neck. Its main job is to regulate the levels of calcium, phosphorus, and vitamin D, which are crucial for maintaining strong bones, proper nerve function, and healthy muscles.

The PTH blood test gives your doctor valuable insights into how well your parathyroid glands are working and whether your body's calcium balance is on track. Let's delve deeper into the PTH test normal range and what it can reveal about your health.

Why Is the PTH Test Done?

Your doctor may order a PTH test if they suspect you have a disorder affecting your parathyroid glands or calcium metabolism. Some common reasons for requesting this test include:

• Investigating the cause of abnormally high or low blood calcium levels
• Diagnosing conditions like hyperparathyroidism (overactive parathyroid glands) or hypoparathyroidism (underactive parathyroid glands)
• Evaluating symptoms that may be related to calcium imbalance, such as:
  • Bone pain or fractures
  • Kidney stones
  • Fatigue and weakness
  • Muscle cramps or twitches
  • Mood changes like depression, irritability or forgetfulness

How to Prepare for the Parathyroid Hormone Test

In most cases, the parathyroid hormone test usually doesn't require any special preparation. You can eat and drink normally before the test, unless your doctor instructs otherwise.

However, it's important to inform your healthcare provider about any medications or supplements you're taking. Some drugs, especially those containing calcium, magnesium, biotin or vitamin D, can affect your PTH test results. Your doctor may advise you to temporarily stop these medications to ensure accurate test readings.

Types of PTH Tests

The most commonly used PTH test purpose measures the ‘intact’ form of parathyroid hormone, which is the biologically active form. This is the biologically active form that directly influences calcium metabolism. The intact parathyroid hormone test is sufficient for most clinical purposes.

In some specialised cases, such as PTH-related peptide (PTHrP), especially in the context of malignancy-related hypercalcemia. However, these tests are less routinely used in medical practice.

How Is the PTH Test Performed?

The parathyroid hormone test is a simple procedure that involves drawing a sample of blood from a vein in your arm. Here's what you can expect during the test:

• The healthcare professional will clean the skin over your vein with an antiseptic solution.
• A needle will be gently inserted into the vein to collect a small amount of blood into a tube.
• Once enough blood is collected, the elastic band will be removed, and a cotton swab or bandage will be placed over the needle site.

The blood sample will then be sent to a laboratory for analysis. You may feel a slight sting when the needle goes in, but the test is usually over in a few minutes with minimal discomfort.

What Do the PTH Test Results Mean?

The PTH test normal range can vary slightly between laboratories, but a typical reference range is 10-65 picograms per milliliter (pg/mL)[2][4]. So, what does it mean if your PTH levels fall outside this range?

• High PTH Levels (Hyperparathyroidism): Elevated PTH levels often point to hyperparathyroidism diagnosis, a condition where your parathyroid glands become overactive and secrete too much PTH.
  • This can be due to a benign tumour (adenoma) on one or more parathyroid glands, enlargement (hyperplasia) of the parathyroid glands, or in rare cases, parathyroid cancer.
  • Excess PTH triggers your bones to release more calcium into the bloodstream, leading to abnormally high blood calcium levels (hypercalcemia). Over time, this can cause problems like osteoporosis, kidney stones, and mental health issues.
  • Sometimes, high PTH occurs as a compensatory response to persistently low blood calcium, often due to vitamin D deficiency or chronic kidney disease. This is called secondary hyperparathyroidism.
• Low PTH Levels (Hypoparathyroidism): On the flip side, low PTH levels may indicate hypoparathyroidism, where your parathyroid glands are underactive and don't produce enough PTH.
  • This can happen due to autoimmune disorders that damage the parathyroid glands, surgical removal of the parathyroid glands, radiation therapy to the neck area, severe magnesium deficiency, or excess calcium intake.
  • Insufficient PTH leads to low blood calcium (hypocalcemia), which can cause symptoms like muscle cramps, tingling sensations, and seizures.

Understanding PTH test normal range and interpreting your PTH test results requires considering other factors like your blood calcium levels and overall health. Your doctor will explain what your specific results mean and recommend the appropriate treatment plan.

Conditions Detected by the PTH Test

The parathyroid hormone test is a valuable tool in diagnosing several conditions related to parathyroid gland dysfunction and calcium imbalances. Some of the key conditions it can help detect include:

• Primary hyperparathyroidism
• Secondary hyperparathyroidism
• Hypoparathyroidism
• Vitamin D deficiency
• Chronic kidney disease
• Certain cancers that affect calcium metabolism, like multiple myeloma or breast cancer

By identifying the underlying cause of your symptoms or abnormal calcium levels, the PTH test paves the way for targeted treatment and better management of your condition.

Related Tests Often Ordered with PTH

To get a complete picture of your parathyroid function and calcium balance, your doctor may order additional tests along with the PTH test. Some common companion tests include:

• Serum calcium (total and ionised): Measures the amount of calcium in your blood
• Serum phosphate: Checks your blood phosphorus levels
• Vitamin D levels: Assesses your body's vitamin D status
• Creatinine: Evaluates your kidney function
• Magnesium levels: Looks for magnesium deficiencies that can affect PTH secretion

These tests work together to provide a comprehensive assessment of your parathyroid and calcium-related health, helping your doctor make an accurate diagnosis and tailored treatment plan.

How to Manage Abnormal PTH Levels

The management of abnormal PTH levels depends on the specific condition diagnosed. Here are some general treatment approaches for common PTH-related disorders:

Primary Hyperparathyroidism

• Surgery to remove the abnormal parathyroid gland(s) is often the definitive treatment.
• If surgery isn't suitable, medications like calcimimetics can help control calcium levels.

Secondary Hyperparathyroidism

• Treatment focuses on correcting the underlying cause, such as vitamin D deficiency or kidney disease.
• Dietary changes, supplements, and medications may be recommended to normalise calcium and PTH levels.

Hypoparathyroidism

• Calcium and vitamin D supplements are the mainstay of treatment to maintain normal blood calcium levels.
• Regular monitoring of calcium, phosphorus, and PTH levels is essential to adjust the treatment as needed.

Conclusion: Why Monitoring PTH Can Safeguard Bone and Kidney Health

The PTH test offers a window into the complex interplay between your parathyroid glands and calcium metabolism. By detecting imbalances early, this simple blood test can help you and your doctor take proactive steps to prevent complications and keep your bones and kidneys healthy for the long haul.

At Metropolis Healthcare, we understand the importance of accessible, reliable diagnostic testing in managing your health. Our team of skilled phlebotomists can collect your blood sample from the comfort of your home, ensuring a hassle-free experience.

FAQs About the PTH Test

What happens when PTH is high?

High PTH levels usually indicate hyperparathyroidism. Excess PTH can lead to high blood calcium, which over time can cause problems like osteoporosis, kidney stones, fatigue, muscle weakness, and depression.

What is the PTH normal range?

The PTH test normal range can vary slightly between labs, but it typically falls between 10-65 picograms per millilitre (pg/mL)[2][4]. Your doctor will interpret your results based on the specific reference range used by the testing laboratory.

Is PTH a tumour marker?

No, PTH is not considered a tumour marker in the traditional sense. While very rarely, high PTH levels can be caused by parathyroid cancer, parathyroid hormone tests are primarily used to diagnose parathyroid gland disorders and calcium imbalances rather than screen for cancer.

What does it mean if my PTH levels are low?

Low PTH levels may indicate hypoparathyroidism or conditions that decrease blood calcium levels. Causes can include autoimmune disorders, surgical removal of the parathyroid glands, radiation therapy, or severe magnesium deficiency. Low PTH can lead to hypocalcemia, causing symptoms like muscle cramps, tingling, and seizures.

What are the symptoms of abnormal PTH levels?

High PTH may cause bone pain, fractures, kidney stones, fatigue, muscle weakness, and mood changes. Low PTH may lead to muscle cramps, tingling, numbness, or seizures due to low blood calcium.

Can PTH levels fluctuate throughout the day?

PTH levels can show mild daily variation over the course of the day, with higher levels typically seen at night and lower levels in the morning.

Is the PTH test painful?

The parathyroid hormone test involves a simple blood draw, which can cause momentary discomfort when the needle is inserted into your vein. Most people tolerate the test with minimal pain.

Can diet affect PTH levels?

Yes, your diet can influence PTH levels to some extent. Consuming very high amounts of calcium or phosphorus can suppress PTH secretion, while a diet low in calcium or vitamin D can stimulate PTH production.