A growth hormone
(GH) test measures the amount of human growth
hormone (GH) in the blood. GH is made by the
pituitary gland and is needed for growth. It plays an
important role in how the body uses food for energy (metabolism).
The amount of GH in the blood changes during the day and is affected by
exercise, sleep, emotional stress, and diet.
Too much GH during
childhood can cause a child to grow larger than normal (gigantism). Too
little GH during childhood can cause a child to grow less than normal (dwarfism). Both conditions can be treated if found
In adults, too much GH is caused by a noncancerous tumor
of the pituitary gland (adenoma). Too much GH can cause bones
of the face, jaw, hands, and feet to grow larger than normal (acromegaly).
Growth hormone can cause the
release of other substances (factors) that affect growth and metabolism. One of
insulin-like growth factor 1 (IGF-1). When the GH
level is very high, the IGF-1 level is also very high. A test for IGF-1 may
also be done to confirm high GH levels.
Why It Is Done
A test for growth hormone (GH) is done
- See whether a child whose growth is abnormal
has dwarfism or gigantism.
- See whether an adult has acromegaly.
This condition is caused by a tumor (adenoma) of the pituitary
- Check treatment that uses growth hormone.
How To Prepare
Do not exercise or eat or drink anything
for 10 hours before the test. You may be asked to sit quietly for 30 minutes
right before the test.
Certain medicines can affect growth hormone
test results, such as
estrogens (including birth control pills). Your doctor may ask you to stop taking these medicines before the test.
How It Is Done
Blood levels of growth hormone (GH) can
change quickly, so more than one blood sample may be taken on different days.
Insulin-like growth factor 1 (IGF-1) levels change more slowly, and it may be
the first test done.
The health professional drawing blood
- Wrap an elastic band around your upper arm to
stop the flow of blood. This makes the veins below the band larger so it is
easier to put a needle into the vein.
- Clean the needle site with
- Put the needle into the vein. More than one needle stick
may be needed.
- Attach a tube to the needle to fill it with
- Remove the band from your arm when enough blood is
- Put a gauze pad or cotton ball over the needle site as
the needle is removed.
- Put pressure to the site and then a