Growth Hormone Tests - Understand the Test & Your Results

What are growth hormone tests?
Growth hormone (GH) tests are blood tests that check if your body is making a normal amount of GH. Hormones are chemical messengers in your bloodstream that control the actions of certain cells or organs. GH, also known as human growth hormone, controls your body's growth. It also helps control metabolism, the process your body uses to make energy from the food you eat. GH is made in the pituitary gland , a small organ at the base of your brain that controls many functions, including growth.
In children, GH plays a major role in bone growth, muscle mass development, and height. In adults, GH affects bone and muscle health. If you or your child have too much or too little GH, it can cause health problems.
GH levels in your blood change throughout the day, depending on your diet and activity levels. So, a standard blood test doesn't usually provide helpful information about GH levels. Instead, GH levels are usually checked in blood tests taken over a few hours that measure other substances, such as proteins and other hormones that are related to GH production. This will provide more accurate results about your or your child's GH levels.
Other names: GH test, human growth hormone test, somatropin test, growth hormone stimulation test, growth hormone suppression test
What are they used for?
GH tests are used to detect and monitor GH disorders, including:
GH deficiency (not enough GH). In children, GH is essential for normal growth and development. A GH deficiency can cause a child to grow more slowly and be much shorter than children of the same age and sex. In adults, GH deficiency can lead to low bone density and reduced muscle mass.
Gigantism. This rare childhood disorder causes your body to produce excess (too much) GH. Children with gigantism are very tall for their age and have large hands and feet.
Acromegaly. This condition affects adults and causes your body to produce too much growth hormone. Adults with acromegaly have thicker than normal bones and enlarged hands, feet, and facial features.
The tests may also be used if other tests show an issue with your pituitary gland. Some conditions, such as pituitary tumors , can cause your body to make too much or too little GH.
Why do I need a growth hormone test?
Your provider may order a GH test if you or your child has symptoms of a GH disorder or to monitor treatment for a GH disorder.
Symptoms of GH deficiency in children include:
Slowed growth rate compared with children of the same age and sex
Shorter height, arms, and legs, and lower weight than children of the same age and sex
Small penis in males
Delayed puberty
Adults with GH deficiency may have symptoms such as fatigue and decreased bone density and muscle mass. But GH testing isn't common for adults, as other disorders are much more likely to cause these symptoms.
Symptoms of GH excess (gigantism) in children include:
Excessive growth compared with children of the same age and sex
Overly large head
Larger than normal hands and feet
Mild to moderate obesity
Symptoms of GH excess (acromegaly) in adults include:
Deep, husky voice
Larger than normal facial features such as lips, nose, and tongue
Excessive sweating and body odor
Thickening of bones
Coarse, oily skin
Irregular menstrual cycles in women
Erectile dysfunction in men
What happens during a growth hormone test?
Your provider may order a GH stimulation or a GH suppression test, depending on whether symptoms show a possible GH deficiency or a GH excess.
A GH stimulation test is used to check for a GH deficiency. During the test:
A health care professional will use a small needle to take a blood sample from a vein in your arm.
After the needle is inserted, a small amount of blood will be collected into a test tube or vial.
Your child (or you) will be given a medicine through an intravenous (IV) line that stimulates (causes) the pituitary gland to make GH.
More blood samples will be taken over the next two hours.
Each sample will be tested to see if GH levels have increased.
A GH suppression test is used to check for a GH excess. During the test:
A health care professional will take a blood sample from a vein in your arm, using a small needle.
After the needle is inserted, a small amount of blood will be collected into a test tube or vial.
You or your child will drink a solution that contains water and glucose (sugar).
Blood samples will be taken every 30 minutes for two hours after drinking the solution.
The blood samples will be tested to see if GH levels have decreased.
Will I need to do anything to prepare for this test?
You may need to fast (not eat or drink) for several hours before your test.
Are there any risks to this test?
There is very little risk to you or your child in having a blood test or getting an IV. There may be slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly. There is no risk to drinking the glucose solution.
What do the results mean?
If GH levels don't increase to a certain level during a GH stimulation test, it may mean that there is a GH deficiency.
If your child is diagnosed with GH deficiency, they may benefit from treatment with GH supplementation. GH supplementation is an injected medicine that contains manufactured human growth hormone. When GH deficiency is diagnosed and treated early, some children can grow several inches in the first year of treatment. Others grow less and more slowly but still benefit from treatment.
If GH levels don't decrease to a certain level during a GH stimulation test, it may mean that there is a GH excess. For your child, this could mean they have gigantism. For you, it may mean you have acromegaly.
Gigantism and acromegaly are most often caused by a tumor in the pituitary gland. Treatment for the tumor may include radiation therapy , surgery, and/or medicine. But if the cause is not a tumor, you or your child may need more tests to identify the cause.
Learn more about laboratory tests, references ranges, understanding results .
Is there anything else I need to know about a growth hormone test?
Your provider may order other blood tests to help diagnose a GH disorder. These can include:
IGF-1 test . IGF-1 is a hormone that helps manage the effects of GH in your body. Unlike GH, IGF-1 levels are more stable throughout the day. So, a reliable way to track GH in your body is by measuring the level of IGF-1 in the blood.
IGBP-3 test. IGBP-3 is a protein that is the main carrier of IGF-1. This test can help diagnose a GH deficiency, GH insensitivity (when your body can't use the growth hormone it makes), or GH excess.
References
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