Growth Hormone Tests

What are growth hormone tests?

Growth hormone (GH) tests are blood tests that check to see if your body is making a normal amount of GH. GH, also known as human growth hormone, is a substance that controls your body's growth. It also helps control metabolism, the process of how your body uses food and energy. GH is made in the pituitary gland, a small organ in the base of the brain.

In children, GH plays a major role in bone growth, development of muscle mass, and height. In adults, GH affects bone and muscle health. If children or adults have too much or too little GH, it can cause health problems.

GH levels in the blood fluctuate 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 tests that measure other substances, such as hormones and proteins, that are related to GH production.

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 diagnose GH disorders, including:

• GH deficiency. 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. In adults, GH deficiency can lead to low bone density and reduced muscle mass.
• Gigantism. This is a rare childhood disorder that causes the body to produce too much GH. Children with gigantism are very tall for their age and have large hands and feet.
• Acromegaly. This disorder, which affects adults, causes the 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 a problem with the pituitary gland.

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.

Symptoms of GH deficiency in children include:

• Slowed growth rate compared with children of the same age
• Shorter height, arms, and legs, and lower weight than children of the same age
• 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
• 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 (not enough GH) or a GH excess (too much GH).

A GH stimulation test is used to check for a GH deficiency. 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.
• Your child (or you) will be given a medicine through an IV line that stimulates the pituitary gland to make GH.
• More blood samples will be taken over the course of about 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).
• Two more blood samples will be taken within one to 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 indicate GH deficiency.

If your child is diagnosed with GH deficiency, he or she 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 suppression test, it may mean your child has gigantism or you have acromegaly.

Gigantism and acromegaly are most often caused by a tumor in pituitary gland, a small organ in the base of the brain that controls many functions, including growth. Treatment for the tumor may include radiation therapy, surgery, and/or medicine. If the disorders were not caused by a tumor, you or your child may need more tests.

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 include:

• IGF-1 test. IGF-1 is a hormone that helps manage GH in the body. Unlike GH, IGF-1 levels remain stable throughout the day. So, it can be a useful way to find out if your body is making a normal amount of GH.
• IGBP-3 test. IGBP-3 is a protein that is the main carrier of IGF-1. This test can help diagnose a GH deficiency or GH excess.