PTH
Alternative Names: Parathormone; Parathormone (PTH) intact molecule; Parathyroid hormone
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.
Why is the Test Performed?
Your doctor may order this test if you have abnormal calcium or phosphorus levels, and a PTH abnormality is suspected.
How is the Test 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.
Preparation for the Test
You should not eat or drink anything except water for 10 to 12 hours before the test.
How will the Test 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.
PTH Risks
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Normal Results for PTH
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.
The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.
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:
Learn more about PTH
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.
Copyright 2011 A.D.A.M., Inc.
