Test Detail
Overview
Interpreting Results
FAQ's

Content created by

Written by
Dr. Shreya Gupta
BDS, MDS - Oral and Maxillofacial Pathology
Reviewed by
Dr. Ashish Ranjan
MBBS, MD (Pharmacology)
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Intact Parathyroid Hormone

(iPTH)
You need to provide
Blood
This test is for
Male, Female
Test Preparation
  1. No special preparation required

Overview


What is iPTH?

Parathyroid hormone (PTH) is a hormone secreted by the parathyroid gland. It helps to maintain the levels of calcium in blood within the normal range. Parathyroid hormone in the blood is found in its biologically active intact form as well as in fragments of various sizes formed after the breakdown of the intact parathyroid hormone. The Intact Parathyroid Hormone Test measures the levels of the intact parathyroid hormone in the blood.

Why is iPTH done?

The Intact Parathyroid Hormone Test is performed:

·         To determine the cause of abnormal calcium levels

·         To help diagnose hyperparathyroidism (excessive secretion of parathyroid hormone) and hypoparathyroidism (low secretion of parathyroid hormone)

·         To monitor surgical treatment for hyperparathyroidism (Intraoperative PTH)



What does iPTH Measure?

The Intact Parathyroid Hormone Test measures the levels of the intact parathyroid hormone in the blood.

The parathyroid hormone is secreted by two pairs of parathyroid glands located behind the thyroid gland. It is secreted when blood calcium levels fall below normal levels (hypocalcemia). Its secretion helps to maintain blood calcium levels in three ways:

·         It stimulates the release of calcium from bones

·         It signals the conversion of Vitamin D from the inactive to the active form in the kidneys since Vitamin D helps in the uptake of calcium from food

·         It also signals the kidneys to reduce excretion of calcium through urine

Parathyroid hormone forms a part of a feedback mechanism which also involves calcium, Vitamin D, phosphate and magnesium. Disruptions in this feedback mechanism affect the normal levels of calcium in the blood and can cause hypercalcemia (high levels of calcium in the blood) or hypocalcemia (low levels of calcium in the blood).

Parathyroid hormone is secreted in a diurnal pattern, with levels reaching their highest during sleep and lowest during midday. Parathyroid hormone secretion also follows a seasonal pattern due to its inverse relationship with Vitamin D. Low levels of Vitamin D are generally observed during winters and in cloudy weather due to low sunlight. This leads to increased secretion of parathyroid hormone to compensate for low Vitamin D. On the other hand, high levels of Vitamin D in summers and sunny weather leads to reduced secretion of parathyroid hormone.

The biologically active complete parathyroid hormone is made up of 84 amino acids and is called intact parathyroid hormone (PTH 1-84). Once released into the blood, it is quickly taken up by the liver and kidneys, and cleaved into fragments of variable sizes called C-terminal fragments. The C-terminal fragments have a longer half-life than the intact hormone and are present in the blood for a longer duration. Levels of the intact hormones are normally lower than the C-terminal fragments but increase in case of calcium deficiency. The Intact Parathyroid Hormone Test measures the levels of the intact parathyroid hormone in the blood.

Interpreting iPTH results


Interpretations

      

Normal range: 14.00 to 72.00 pg/ml

Reference range may vary in different labs.


Intact Parathyroid Hormone Test is performed together with Blood Calcium Test to determine the cause of calcium deficiency and the results are interpreted as follows:

Calcium

PTH

Interpretation

Normal

Normal

Blood calcium regulation normal

Low

High

Parathyroid gland normal, low Calcium levels are due to other causes

Low

Normal/Low

PTH secretion low, hypoparathyroidism may be indicated

High

High

Hyperparathyroidism may be indicated

High

Low

Parathyroid gland normal, high Calcium levels are due to other causes

Normal

High

Mild hyperparathyroidism

Answers to Patient Concerns & Frequently Asked Questions (FAQs) about iPTH


Frequently Asked Questions about Intact Parathyroid Hormone

Q. How is this test performed?
This test is performed on a blood sample. A syringe with a fine needle is used to withdraw blood from a blood vessel in your arm. The healthcare provider will tie an elastic band around your arm to make the blood vessels swell with blood. This makes it easier to withdraw blood. You may be asked to tightly clench your fist. Once the veins are clearly visible, the area is cleaned with an antiseptic solution and then the needle is inserted into the blood vessel to collect the sample. You will feel a tiny pinprick during the procedure. Blood sample once collected will then be sent to the laboratory.
Q. Is there any risk associated with this test?
There is no risk associated with the test. However, since this test involves a needle prick to withdraw the blood sample, in very rare cases, a patient may experience increased bleeding, hematoma formation (blood collection under the skin), bruising or infection at the site of needle prick.
Q. What is Hypocalcemia?
Hypocalcemia is a condition where the blood calcium levels are below the normal range. This may occur due to: · Low levels of blood protein, especially albumin · Hypoparathyroidism or reduced secretion of parathyroid hormones · Genetic resistance to parathyroid hormones · Dietary deficiency of calcium · Intolerance of dietary calcium · Vitamin D deficiency · Magnesium deficiency · High phosphorus concentration in blood · Acute pancreatitis (inflammation of pancreas) · Hormonal changes in women after menopause · Renal failure · Alcoholism
Q. What are the symptoms of Hypocalcemia?
Short term or mild deficiency of calcium usually produces very little symptoms. This happens because the body can augment mild calcium deficiency by releasing the calcium stored in bones. Symptoms appear in case of chronic or long term calcium deficiency. Symptoms of Hypocalcemia include: · Weak and brittle hairs · Brittle nails · Thin and brittle bones which fracture easily · Confusion · Memory loss · Numbness and tingling sensation · Muscle spasms and cramps · Depression · Hallucinations · Seizures
Q. What is Hypercalcemia?
Hypercalcemia is the condition where blood calcium levels rise higher than the normal range. This may occur due to: · Hyperparathyroidism or increased secretion of parathyroid hormones · Hyperthyroidism or increased secretion of thyroid hormones · Prolonged period of immobility as in bed rest · Sarcoidosis, a condition that produces nodules in different organs · Tuberculosis · Overconsumption of Vitamin D · Treatment by thiazide diuretics · Kidney transplant · HIV/AIDS · Cancer
Q. What are the symptoms of Hypercalcemia?
Symptoms of Hypercalcemia include: · Headache · Weakness and fatigue · Excessive urination and thirst · Nausea · Pain in abdomen · Constipation · Abnormal heartbeat or cardiac arrhythmia · Weak and brittle bones · Muscular cramps · Depression and irritability · Confusion · Coma
Q. Is there any preparation required before the Intact Parathyroid Hormone test?
A fasting period of 10 hours is advised before the test is performed. Inform the doctor of any medications you may be taking. No other specific preparations are usually required before the Intact Parathyroid Hormone Test.
Q. What additional tests can be prescribed by your doctor in case the result of parathyroid hormone test is not normal?
Additional tests that may be prescribed in case of abnormal Intact Parathyroid Hormone test result are: · Blood Calcium Test · Electrolyte Panel Test · Kidney Function Tests
Q. What factors can affect the Intact Parathyroid Hormone test result?
Factors that can affect the Intact Parathyroid Hormone Test include: · High body fat content · Deficiency of Vitamin D · Burnett’s Syndrome · Certain medications like vitamin supplements containing Vitamins A and D, phosphates, steroids, etc.
Q. What are the common causes of decreased parathyroid hormone levels?
Common causes of hypoparathyroidism include: · Reduced activity of parathyroid glands · Increased hormone secretion from thyroid gland (hyperthyroidism) · Deficiency of magnesium · Hypercalcemia unrelated to parathyroid gland
Q. What are the common causes of increased parathyroid hormone levels?
Common causes of hyperparathyroidism include: · Increased activity of parathyroid glands, usually due to parathyroid gland tumors · Improper response of the kidneys to PTH · Deficiency of Vitamin D · Injury to the spinal cord · Hypocalcemia unrelated to parathyroid gland
Q. What is Intraoperative PTH?
Hyperparathyroidism is usually treated by surgically removing the affected parathyroid gland to reduce parathyroid hormone secretions. Enough parathyroid gland tissues are left behind to prevent hypoparathyroidism. The Intraoperative PTH is a test for the intact parathyroid hormone, performed during such a surgery to ensure all of the abnormal parathyroid gland tissues are removed. PTH levels are checked before and after the surgical removal of the abnormal gland tissues. Since PTH has a very short half-life of about 5 to 10 minutes, successful surgical removal of abnormal tissues of the gland causes the PTH levels in the blood to drop by 50% within 5 to 10 minutes. The test is performed and the result is analyzed during the surgery to determine the extent of tissue to be removed.
Q. How does Parathyroid hormone affect the levels of Phosphorus in blood?
Apart from calcium, the parathyroid hormone also plays a role in the regulation of phosphate levels in the blood. Parathyroid hormone increases phosphate excretion through urine by reducing its reabsorption in the kidneys. Parathyroid hormone increases phosphate absorption from the intestines but the overall effect of parathyroid hormone leads to a small decrease in the levels of phosphate in the blood.
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