GH suppression test; Glucose loading test; Acromegaly - blood test; Gigantism - blood test DefinitionThe growth hormone suppression test determines whether growth hormone (GH) production can be suppressed by taking a specific amount of glucose (called a glucose load). How the Test is PerformedAt least three blood samples are taken. The test is done in the following way:
How to Prepare for the TestDo not eat anything and limit physical activity for 10 to 12 hours before the test. You may also be told to stop taking medicines that can affect the test results. These medicines include glucocorticoids such as prednisone, hydrocortisone, or dexamethasone. Check with your health care provider before stopping any medicines. You will be asked to relax for at least 90 minutes before the test. This is because exercise or increased activity can change GH levels. If your child is to have this test done, it may be helpful to explain how the test will feel and even demonstrate on a doll. The more familiar your child is with what will happen and why, the less anxiety the child will feel. How the Test will FeelWhen the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away. Why the Test is PerformedThis test checks to see if a high level of GH can be suppressed by taking a glucose load. If it cannot, this may lead to gigantism in children and acromegaly in adults. It is not used as a routine screening test. This test is only done if you show signs of increased GH. Normal ResultsNormal test results show a GH level of less than 1 ng/mL. In children, GH level may be increased due to reactive hypoglycemia. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results. What Abnormal Results MeanIf the GH level is not changed and stays high during the suppression test, your provider will suspect gigantism or acromegaly. You may need to be retested to confirm the test results. RisksThere is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others. Risks of having blood drawn are slight, but may include:
ReferencesKaiser U, Ho K. Pituitary physiology and diagnostic evaluation. In: Melmed S, Auchus RJ, Goldfine AB, Koenig RJ, Rosen CJ, eds. Williams Textbook of Endocrinology. 14th ed. Philadelphia, PA: Elsevier; 2020:chap 8. Melmed S. Acromegaly. In: Robertson RP, ed. DeGroot's Endocrinology. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 6. | |
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Review Date: 11/6/2023 Reviewed By: Neil K. Kaneshiro, MD, MHA, Clinical Professor of Pediatrics, University of Washington School of Medicine, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. No warranty of any kind, either expressed or implied, is made as to the accuracy, reliability, timeliness, or correctness of any translations made by a third-party service of the information provided herein into any other language. © 1997- A.D.A.M., a business unit of Ebix, Inc. Any duplication or distribution of the information contained herein is strictly prohibited. | |
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Blood test
