The growth hormone stimulation test, growth hormone test, or simply the GH test aims at measuring the amount of growth hormones present in a person’s body mainly the blood stream. This test is usually performed after a patient has been given medication that would generate growth hormones in the body. The test can also help measure the functioning of especially the pituitary gland and its ability to release growth hormones.
A person who is experiencing a deficiency of growth hormones or has an unnaturally short or large stature, is usually recommended this test. Since this is a blood test, a sample of blood is taken, usually from the arm. A trained nurse or a technician will usually insert a needle and collect the sample with the help of an injection. A total of five samples are taken at varying intervals. Since the amount of growth hormones in the blood is not consistent at any given point in time, several samples are taken to measure trends and derive an average. The primary sample is usually taken in the early morning, after which a dose of arginine, which helps stimulate the production of growth hormones, is injected into the vein. After the medicine is injected, four more samples are taken, every thirty minutes.
Though there are not many precautions that need to be taken before this test, it is advisable to tell the doctor in advance if you are suffering from any kind of disease involving the liver or the kidney. This is because the arginine which is injected into the vein could cause severe risks and other problems in case of such disorders.
The amounts of GH present in the blood are volatile and therefore doctors recommend that you should limit any kind of physical activity at least 12 hours prior to the test. During this period, you are also advised to fast. Depending on your health conditions, your doctor may also ask you to avoid the intake certain medicines for a few days.
Since the amount of GH in the blood keeps varying throughout the day, the test results consider peak values, intermediate values, and subnormal values of GH. The standard or acceptable peak value throughout the day is 10 ng/ml or more. If the GH amount is less than 5 ng/ml, it is considered subnormal. Anything in between is an intermediate value. The normal values may vary amongst laboratories and therefore, a doctor should be consulted for a correct diagnosis.
Abnormal test results simply indicates a deficiency of growth hormones. In adults specifically, abnormal test results are related to a disorder known as panhypopituitarism.