Growth hormone (GH), also known as human growth hormone (HGH) or somatotropin, is one of several hormones produced by the pituitary gland in your brain. GH plays a crucial role in normal human growth and development, especially in children and adolescents. GH levels that are higher or lower than they should be can lead to health problems in both children and adults.
A serum growth hormone test (GH test) is used to measure the amount of GH in your blood. It is not a routine blood test, since abnormalities of GH are uncommon. If your doctor has a strong suspicion that you have hormonal abnormalities, they will use the test to confirm a diagnosis and guide management. Finding any GH problems can help treatment be more effective.
Doctors can accurately measure the levels of some hormones in your blood simply by drawing a sample and analyzing it in the lab. However, GH testing is not so simple. Finding the level of the hormone at a single point in time doesn’t always help your doctor make a diagnosis because levels of this hormone naturally rise and fall throughout the day. This is why more specialized GH tests are usually used.
Your doctor will likely order either a growth hormone suppression test or a growth hormone stimulation test, depending on whether your doctor suspects that you’re producing too much or too little growth hormone. Frequently, an insulin-like growth factor-1 test (IGF-1 test) is also ordered. If you have an excess or a deficiency of GH, you will also have higher or lower than normal levels of IGF-1. The key advantage of examining IGF is that, unlike GH, its levels remain stable.
Preparation and Testing
It’s important to follow all preparation instructions. Your doctor may ask you to:
- fast for several hours before the test
- take a prescription medication a few days prior to the test
- exercise before the test
- stop taking medicines that may affect the test results (check with your doctor on which specific drugs)
The test itself is fairly routine and carries little discomfort or risk. A healthcare professional will use a needle to collect one or more blood samples. You may be asked to drink a solution, or you may be given one through an IV, to see how your body responds. A lab will process your blood samples to determine whether your body is producing more or less GH than it should.
GH testing may be ordered for children when they show signs of a growth hormone deficiency (GHD). These include:
- delayed growth and bone development
- delayed puberty
- short stature
A GHD isn’t usually the cause for a child’s short stature or slow growth. GHD is rare, and a child’s below average height can often be attributed to other causes, including simple genetics inherited from their parents.
GH testing may also be performed if there are signs that a child’s body is producing too much GH. This can result in a very rare condition known as gigantism, in which the long bones do not stop growing at the end of puberty. People with this condition can grow to heights of 7 feet or more.
Adult bodies rely on GH to maintain muscle mass and bone density and to regulate the metabolism of fats. Too little GH can reduce bone density and muscle mass and disrupt fat levels. However, this is very rare. Extra GH in adults can cause the bones to thicken, a symptom associated with a condition called acromegaly. Left untreated, acromegaly can have a number of complications, including a higher risk of arthritis and heart problems.
Your doctor will determine the appropriate course of treatment if testing indicates that there is a problem with your GH levels. This treatment may involve medication, surgery, radiation, or a combination of these approaches. Synthetic growth hormone is often prescribed to those with growth hormone deficiencies.
Regardless of your age or the nature of your GH abnormality, early detection is very important to increase your chances of a good outcome.