Parathyroid Hormone

Other names: Parathormone; PTH; Intact PTH

The parathyroid hormone helps to regulate calcium levels in the blood; it is division of a system, which involves calcium, PTH, vitamin D, phosphate and magnesium. If a division of the system is damaged or affected by a health condition, this may cause the levels of calcium in the blood to become abnormal.

PTH is fashioned by four parathyroid glands, which are found in the neck; the glands usually secrete PTH into the blood when levels of calcium in the blood are lower than normal. In reaction to low levels of calcium, the parathyroid glands work to raise the levels; it does this by taking calcium from the bones, stimulating the vitamin D stored in the kidneys and reducing the emission of calcium into the urine.

When is the test used?

The test is used primarily to find out why levels of calcium are higher or lower than normal; the test is also used to determine whether abnormal calcium levels are caused by issues relating to the parathyroid gland.

The test is usually ordered when a patient has abnormal calcium levels in their blood; the test may be conducted when the patient has symptoms of hypocalcaemia, including:

  • Muscle cramps
  • Muscle ache
  • Tingling in the fingers

The test will also be ordered if the patient has symptoms of hypercalcaemia, including:

  • Tiredness
  • Nausea
  • Vomiting
  • Abdominal pain
  • Constant thirst

The test is also ordered when the patient has started a course of treatment; the results of the test help the doctor to gauge if the treatment is working.

How is the test performed?

The test is done by collecting and analysing a sample of the patient’s blood; a needle is inserted into the vein (usually on the inside of the elbow, as veins are usually more prominent here) and the blood is drawn out and collected in a syringe. Once the doctor (or nurse) has a sufficient sample, the blood will be bottled, labelled with the patient’s name and sent to the laboratory for testing.

What do the test results show?

The results of the PTH test should be examined alongside the results of a calcium test.

If both calcium and PTH levels are normal, this indicates that calcium regulation is effective.

If levels of PTH are lower than normal, this may be caused by hyperparathyroidism (which may be caused by other health conditions) or conditions which cause hypercalcaemia.

High levels of PTH are usually associated with hyperparathyroidism, which is usually caused by a benign parathyroid tumour.

If levels of calcium are low and levels of PTH are high, this means the body is working effectively to address the low concentration of calcium.

If calcium levels are low and the level of PTH is either normal or low, this means that the body is not working to correct the level of calcium and this may indicate that the parathyroid gland is not as active as it should be (hypoparathyroidism).

If both calcium and PTH levels are high, this usually means that the parathyroid glands are producing too much PTH.

Specific Blood Tests

Blood Test Guide

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