Anti-human GH antibodies, growth hormone neutralizing antibodies
This test looks for growth hormone (GH) antibodies in your blood.
GH is used to manage height issues linked to a growth hormone deficiency. If your body makes GH antibodies in response to GH treatment, the treatment may not work the way it should.
You might have this test if your doctor suspects that your GH treatment isn't working anymore. The most common symptom of GH antibodies is a lack of growth even with adequate doses of GH.
Children with GHD often fail to grow on a normal schedule. Signs include an abnormal weight-to-height ratio and immature facial structure, notably a large forehead and an underdeveloped nose bridge. A child's voice may not mature, his or her hair may not grow well, and the transition to adolescence is often delayed.
Ten to 20 percent of people who get GH therapy will develop GH antibodies in reaction to it. This often happens soon after GH treatment starts – usually after a three- to six-month growth period. The antibodies can cause the treatment to not work.
The good news is that GH antibodies are becoming increasingly rare thanks to the use of a synthetic, or man-made, growth hormone.
Your doctor may also order a blood test for insulin-like growth factor I (IGF-I). Low levels of IGF-I can be a sign that the GH may not be working the way it should.
Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.
Normal results are negative, meaning that no GH antibodies were found. Positive results mean that GH antibodies were found and that your GH therapy may no longer be working.
The test requires a blood sample, which is drawn through a needle from a vein in your arm.
Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.
Other factors aren't likely to affect your results.
You don't need to prepare for this test.