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Growth hormone suppression test

GH suppression test; Glucose loading test; Acromegaly - blood test; Gigantism - blood test

The growth hormone suppression test determines whether growth hormone (GH) production is being suppressed by high blood sugar.

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Blood test

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How the Test is Performed

At least 3 blood samples are taken.

The test is done in the following way:

How to Prepare for the Test

DO 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 Feel

When 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 Performed

This test checks for a high level of GH, a condition that leads 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 Results

Normal 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 Mean

If the GH level is not changed and stays high during the suppression test, the provider will suspect gigantism or acromegaly. You may need to be retested to confirm the test results.

Risks

Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight, but may include:

Related Information

Blood sugar test
Gigantism
Acromegaly

References

Kaiser U, Ho KKY. Pituitary physiology and diagnostic evaluation. In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology. 13th ed. Philadelphia, PA: Elsevier; 2016:chap 8.

Nakamoto J. Endocrine testing. In: Jameson JL, De Groot LJ, de Kretser DM, et al, eds. Endocrinology: Adult and Pediatric. 7th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 154.

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Review Date: 10/18/2017  

Reviewed By: Neil K. Kaneshiro, MD, MHA, Clinical Professor of Pediatrics, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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