PTH
Definition
PTH stands for parathyroid hormone. It is a protein hormone released by the parathyroid gland. PTH is the most important regulator of the body's calcium and phosphorus levels.
Release of PTH is controlled by the level of calcium in the blood. Low blood calcium levels cause increased PTH to be released, while high blood calcium levels inhibit PTH release.
A laboratory test can be done to measure the amount of PTH in your blood.
Alternative Names
Parathormone; Parathormone (PTH) intact molecule; Parathyroid hormone
How the Test is Performed
Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.
Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.
Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.
How to Prepare for the Test
You should not eat or drink anything except water for 10 to 12 hours before the test.
How the Test Will Feel
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the Test is Performed
Your doctor may order this test if you have abnormal calcium or phosphorus levels and a PTH abnormality is suspected.
Normal Results
Normal values are 10-55 picograms per milliliter (pg/mL). Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
What Abnormal Results Mean
Greater-than-normal levels may occur with:
- Chronic kidney failure
- Familial hypocalciuric hypercalcemia (FHH)
- High phosphate levels (hyperphosphatemia)
- Hyperparathyroidism
- Increased blood lipids
- Malabsorption syndrome
- Osteomalacia in adults
- Pregnancy or breastfeeding
- Pseudohypoparathyroidism
- Rickets in children
- Use of certain medications such as rifampin, anticonvulsants, diuretics, lithium, and those containing phosphate
- Vitamin D deficiency
Lower-than-normal levels may occur with:
- Accidental removal of parathyroid glands during neck surgery
- Autoimmune destruction of parathyroid gland
- Hypomagnesemia
- Hypoparathyroidism
- Metastatic bone tumor
- Milk-alkali syndrome (taking too much calcium)
- Radiation to the parathyroid glands
- Sarcoidosis
- Vitamin D intoxication
Other conditions under which the test may be performed:
- Multiple endocrine neoplasia (MEN) II
- Multiple endocrine neoplasia (MEN) I
- Secondary hyperparathyroidism
Risks
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
References
Wysolmerski JJ, Insogna KL. The parathyroid glands, hypercalcemia, and hypocalcemia. In: Kronenberg HM, Schlomo M, Polansky KS, Larsen PR, eds. Williams Textbook of Endocrinology. 11th ed. St. Louis, MO: WB Saunders;2008:chap 266.
Reviewed By: Ari S. Eckman, MD, Division of Endocrinology and Metabolism, Johns Hopkins School of Medicine, Baltimore, MD. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
