Growth hormone (GH) testing measures the level of human growth hormone in the blood. GH is made in the pituitary gland in the brain. It is needed for growth and development in children. It also helps regulate how the body makes energy, red blood cells, and muscle mass.
There are two types of the test. A GH stimulation test helps diagnose GH deficiency and an underactive pituitary gland. A GH suppression is not as common. It helps diagnose GH excess.
There are many things that can cause problems with GH testing. Stress, exercise, certain medicines, and blood glucose levels can all cause GH levels to rise and fall. This is why GH tests are often done with other hormone tests, such as insulin-like growth factor-1 ( IGF-1).
Reasons for Test
Testing may be done to:
- Find out whether a person has too little GH, which may point to short stature or delayed puberty or bone development
- Find out whether a person has too much GH (less common), which may point to problems like gigantism or acromegaly
- Test how well the pituitary gland is working
- Monitor how well a treatment for excess GH is working
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There are no major problems associated with this test.
What to Expect
Prior to Test
The care team will meet with you to talk about:
- Avoiding food and drink 10 to 12 hours before the test
- Reducing physical activity for 10 to 12 hours before the test
- Current medicines, herbs, and supplements that you take and whether you need to stop taking them before the test
- Resting and avoiding physical activity for ninety minutes before the test
Description of Test
To Collect Blood
An area on the arm will be cleaned with a wipe. A large band will be tied around the arm. The needle will be put in a vein. A tube will collect the blood from the needle. The band will be taken off. After the blood is collected, the needle will be removed. Gauze will be held on the site to help stop bleeding. A bandage may be put over the area.
A blood sample will be taken between 6 am and 8 am. You will be asked to drink a water and glucose (sugar) solution. The glucose should make the GH level in the blood lower. Two more blood samples are taken within 1 to 2 hours of drinking the solution. In each blood sample, the GH level will be measured. IGF-1 levels may also be measured since they do not vary so much.
Insulin Tolerance Test
Blood samples will be drawn 5 times at different intervals. A first sample for blood glucose, cortisol, and growth hormone will be taken between 6 am and 8 am. Then, insulin will be given through the IV. The insulin should make the blood glucose level go down, which should make the GH level go up. Blood samples will be collected at 30, 60, 90, and 120 minutes for glucose, cortisol, and growth hormone.
If the blood sugar has not dropped to a certain level after 45 minutes, a repeat dose of insulin will be given. The blood sample will be collected 75 minutes and 150 minutes later. If the blood sugar levels fall too low, a high dose of sugar will be given by IV, followed by a sugar infusion.
You will be able to leave after the test is done.
How Long Will It Take?
Will It Hurt?
There may be discomfort at the injection site(s). This will go away in about a day. Medicine and home care can help.
Talk to your doctor about your test results. More testing or treatment may be needed.
Call Your Doctor
After the test, call your doctor for:
- Signs of infection, such as fever and chills
- Severe redness, pain, or drainage from the injection site
If you think you have an emergency, call for medical help right away.
Healthy Children—American Academy of Pediatrics
Hormone Health Network—Endocrine Society
About Kids Health—The Hospital for Sick Children
Caring for Kids—Canadian Paediatric Society
Growth hormone. Lab Tests Online—American Association for Clinical Chemistry website. Available at: https://labtestsonline.org/tests/growth-hormone. Accessed September 7, 2021.
Growth hormone deficiency in adults. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/growth-hormone-deficiency-in-adults-11. Accessed September 7, 2021.
Growth hormone deficiency in adults. Hormone Health Network—Endocrine Society website. Available at: https://www.hormone.org/diseases-and-conditions/growth-hormone-deficiency. Accessed September 7, 2021.
Growth hormone deficiency in children. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/growth-hormone-deficiency-in-children. Accessed September 7, 2021.
Growth hormone deficiency in children. Endocrine Society Hormone Health Network website. Available at: http://www.hormone.org/questions-and-answers/2011/growth-hormone-deficiency-in-children. Accessed September 7, 2021.
Growth hormone test (arginine/clonidine stimulation test).Cincinnati Children's website. Available at: https://www.cincinnatichildrens.org/health/g/growth-hormone. Accessed September 7, 2021.
Last reviewed July 2021 by EBSCO Medical Review Board Kari Kuenn, MD Last Updated: 9/8/2021