What To Think About

• Normal levels of growth hormone (GH) change during the day so other tests may be done to confirm the results of a GH test. Other tests can show whether low levels of GH (which can be normal) mean the pituitary gland is not working correctly.
  • IGF-1 blood levels are often done at the same time as a GH test. A high level of IGF-1 with a high level of GH generally means acromegaly is present. In this case, magnetic resonance imaging (MRI) is done to look at the pituitary gland. For more information, see the topic Magnetic Resonance Imaging (MRI) of the Head.
  • The growth hormone suppression test (also called the glucose loading test) measures the level of GH in the blood before and after a person drinks fluid with a large amount of sugar (glucose) in it. Normally, the amount of GH drops to less than 1 ng/mL after drinking the glucose. Levels of GH that stay high may mean acromegaly is present.
  • The growth hormone stimulation test measures the level of GH in the blood before and after insulin or arginine is given in a vein (intravenously) in the arm. No detectable growth hormone can be found for people with normal pituitary function. A growth hormone stimulation test may be used to see if a person lacks GH. Normally, the amount of GH increases after insulin or arginine. A GH level that does not increase after the insulin or arginine is given may mean the person lacks growth hormone.