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PTH (Parathyroid Hormone)

About the test
What is this test done for?
PTH levels in the blood may be measured to determine the presence of hyperparathyroidism and its possible role in abnormal calcium levels.
Why is it Done?
PTH levels are helpful in identifying the underlying cause of calcium level deficit or excess in the body. This may help in tracing hyperparathyroidism, parathyroid tumors, vitamin D deficiency, kidney disease, and some tumors that produce the hormone. Intraoperative PTH assays performed during parathyroid tumor surgery may help in determining if the PTH-producing adenoma was correctly removed.
When should it be performed?
PTH may be ordered if you have conditions such as high calcium level or low phosphorus level in your blood, unexplained severe osteoporosis, or kidney disease.
How is it done
A blood sample will be collected from a vein in your arm. Fasting is not needed prior to sample collection.

The reference range for PTH is as follows: 

  • Normal: 10-65 pg/mL or 10-65 ng/L
  • A higher than normal value may be suggestive of disorders that increase phosphate or phosphorous levels in the blood, such as lack of calcium, which may be due to not consuming enough calcium, ill absorption of calcium in the gut, or losing too much calcium in your urine; swelling in the parathyroid glands, (called primary hyperparathyroidism); tumors in the parathyroid gland, called adenomas; or vitamin D disorders and chronic kidney disease.
  • A lower than normal value may occur with autoimmune destruction of the parathyroid gland; hypoparathyroidism; low magnesium levels in the blood; excess calcium levels; or excess vitamin D intake.
  • Also, in intraoperative PTH assays, a drop of more than 50% of the preoperative level 10 minutes after gland removal can be a confirmation that the correct gland with the PTH-producing adenoma was removed.
Other Tests
PTH may be drawn and interpreted along with serum calcium, phosphorus, magnesium, vitamin D, and urine calcium levels.
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