Medical infographic showing Intact Parathyroid Hormone (iPTH) with four points: calcium balance regulation, vitamin D activation, kidney calcium reabsorption, and calcium release from bones.

iPTH Test: Function, High/Low Levels, Symptoms & Normal Range

1 Comment / Hormones, Explore All Tests / By

Intact Parathyroid Hormone (iPTH) Test: Role, High/Low Levels, Symptoms & Medical Guide

What Is Intact Parathyroid Hormone (iPTH)?

The Intact Parathyroid Hormone (iPTH) test measures the concentration of parathyroid hormone circulating in the bloodstream. PTH is a critical hormone responsible for maintaining stable levels of calcium, phosphorus, and vitamin D—three minerals essential for proper bone strength, nerve activity, muscle contraction, and kidney function. Even slight abnormalities in PTH can create noticeable changes in how the body functions, which is why the test is widely used in endocrine and kidney disorder evaluations.

Doctors commonly order an iPTH test when they suspect:

  • Hyperparathyroidism (excess PTH)
  • Hypoparathyroidism (low PTH)
  • Vitamin D deficiency
  • Chronic kidney disease–related mineral imbalance
  • Calcium or phosphorus abnormalities
  • Bone disorders such as osteoporosis or osteomalacia

Because PTH works closely with the kidneys, bones, and vitamin D pathways, the iPTH test is often paired with blood calcium, phosphorus, and vitamin D levels for an accurate diagnosis.

Where Is iPTH Produced in the Body?

iPTH is produced exclusively by the parathyroid glands. These glands are small, pea-sized structures located behind the thyroid gland in the neck. Most people have four parathyroid glands, although some individuals have more due to natural variation.

The parathyroid glands continuously monitor blood calcium levels. When calcium decreases, the glands release PTH to restore balance. When calcium rises, PTH decreases. This tight regulation keeps nerves, muscles, and bones working properly throughout the day.

Main Functions and Importance of iPTH

1. Maintains Blood Calcium Levels

The most important role of PTH is to prevent calcium from dropping too low. Calcium is essential for:

  • Muscle contraction
  • Heart rhythm
  • Blood clotting
  • Nerve signaling

Whenever calcium decreases, PTH immediately increases to correct the imbalance.

2. Activates Vitamin D

PTH stimulates the kidneys to convert inactive vitamin D into its active form, calcitriol. Active vitamin D helps the intestines absorb more calcium, ensuring the body has a stable supply.

3. Reduces Calcium Loss Through Kidneys

PTH instructs the kidneys to retain calcium instead of excreting it. This allows the body to conserve calcium during deficiency.

4. Releases Stored Calcium From Bones

If dietary intake is low or absorption is poor, PTH triggers the bones to release calcium into the blood. This ensures normal calcium levels but may weaken bones if PTH stays elevated for long periods.

5. Controls Phosphorus Levels

PTH increases phosphorus excretion through urine. This maintains a healthy calcium–phosphate balance, which is essential for bone mineralization and metabolic stability.

Collectively, these functions make iPTH vital for bone strength, muscle activity, nerve communication, and kidney health.

Causes of Low iPTH Levels

Low iPTH levels typically result in hypocalcemia, meaning low blood calcium. Several conditions may cause reduced PTH:

1. Hypoparathyroidism

This is the most common cause of low PTH. It can occur from:

  • Thyroid or neck surgery
  • Autoimmune disorders
  • Congenital absence of parathyroid glands

2. Low Magnesium Levels

Magnesium is essential for PTH secretion. Without adequate magnesium, the parathyroid glands cannot function properly.

3. Vitamin D Toxicity

High levels of vitamin D suppress PTH production because the body detects sufficient calcium absorption.

4. Genetic or Chronic Hypocalcemia

Some rare disorders disrupt calcium regulation and lead to low PTH levels.

Symptoms of Low iPTH Levels

Low PTH causes calcium levels to fall, resulting in symptoms such as:

  • Muscle cramps or spasms
  • Tingling in lips, hands, and feet
  • Painful muscle contractions (tetany)
  • Seizures in severe cases
  • Dry skin and brittle nails
  • Hair fall
  • Fatigue and irritability
  • Mood disturbances

These symptoms occur because calcium is essential for nerve and muscle stability.

Causes of High iPTH Levels

High iPTH levels can be due to disorders of the parathyroid glands, kidney disease, or nutritional deficiencies.

1. Primary Hyperparathyroidism

This condition occurs when one or more parathyroid glands become overactive. Causes include:

  • Parathyroid adenoma (benign tumor)
  • Parathyroid gland enlargement (hyperplasia)

This typically results in high calcium and high PTH.

2. Secondary Hyperparathyroidism

The most common cause of high PTH, especially in:

  • Chronic Kidney Disease (CKD)
  • Severe vitamin D deficiency
  • Calcium deficiency
  • Malabsorption syndromes

In this condition, calcium is low or normal, and PTH rises to compensate.

3. Tertiary Hyperparathyroidism

Long-standing CKD can cause permanent parathyroid overactivity, leading to extremely high PTH levels even when calcium normalizes.

4. Gastrointestinal Malabsorption

Diseases that impair nutrient absorption, such as celiac disease or pancreatitis, may lead to calcium and vitamin D deficiencies, triggering elevated PTH.

Symptoms of High iPTH Levels

High PTH can weaken bones and increase blood calcium, leading to symptoms involving the skeletal system, kidneys, digestive tract, and overall energy levels.

Bone Symptoms

  • Bone pain or tenderness
  • Early osteoporosis
  • Fragile bones
  • Increased fracture risk

Kidney Symptoms

  • Kidney stones
  • Increased urination
  • Excessive thirst

Digestive Symptoms

  • Abdominal discomfort
  • Nausea or vomiting
  • Constipation

General Symptoms

  • Fatigue
  • Depression or mood changes
  • Memory problems
  • Muscle weakness
  • Confusion in severe hypercalcemia

Symptoms vary depending on the underlying cause and whether calcium levels are high or low.

Reference Ranges

Typical values (may vary by laboratory):

Normal iPTH: 10–65 pg/mL

Interpretation should always consider calcium, phosphorus, vitamin D, and kidney function. PTH alone cannot diagnose the condition without these supporting values.

Sample Type

  • Blood sample (serum or plasma)
  • Often collected in EDTA tubes if required by the laboratory

Test Preparation

  • Fasting is not necessary
  • Avoid high-calcium meals before testing
  • Inform your doctor about vitamin D or calcium supplements
  • Discuss kidney-related medications such as diuretics or phosphate binders
  • Stop biotin supplements at least 24 hours beforehand (may interfere with results)

When to Consult a Doctor

Consult a doctor if you experience:

Low Calcium Symptoms

  • Tingling in extremities
  • Muscle cramps or spasms
  • Seizures
  • Sudden weakness

High Calcium Symptoms

  • Excess thirst
  • Frequent urination
  • Bone or abdominal pain
  • Kidney stone symptoms

Patients Requiring Routine Monitoring

  • Chronic kidney disease (especially stages 3–5)
  • Post-thyroid or neck surgery
  • Known parathyroid disorders

Abnormal iPTH levels should be evaluated by an endocrinologist or nephrologist, depending on the suspected cause.

Important Word Explanations

Parathyroid Glands: Small glands behind the thyroid that regulate calcium.
Hyperparathyroidism: Excess PTH production.
Hypoparathyroidism: Low PTH production.
Hypocalcemia: Low calcium in blood.
Hypercalcemia: High calcium in blood.
Calcitriol: Active form of vitamin D made in the kidneys.
Malabsorption: Poor nutrient absorption in the intestines.

~END~

1 thought on “iPTH Test: Function, High/Low Levels, Symptoms & Normal Range”

Leave a Comment

Your email address will not be published. Required fields are marked *