Growth hormone (GH), also known as human growth hormone (HGH) or somatotropin, is one of several hormones produced by the pituitary gland of the brain. Growth hormone plays a crucial role in normal human growth and development. GH levels that are higher or lower than they should be can lead to health problems in both children and adults.
GH is not a routine blood test, and abnormalities of GH are uncommon. If your doctor has a strong suspicion that hormonal abnormalities exist, he or she will use the test to confirm a diagnosis and guide management. Early detection of GH problems often allow effective treatment.
Doctors can accurately measure the levels of some hormones in the 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 is not a highly effective way to 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. A person who has an excess or a deficiency of GH 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.
Regardless of the type of growth hormone testing that is ordered, it is 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 test results
The growth hormone test itself is fairly routine and carries little discomfort and risk. A healthcare professional will use a needle to collect one or more blood samples. You may be asked to drink a solution or will be given one through an IV to see how your body responds. A lab will process these samples to determine whether your body is producing more or less growth hormone than it should.
GH testing may be ordered for children when they show signs of a growth hormone deficiency. These include:
- delayed growth and bone development
- delayed puberty
- short stature
A growth hormone deficiency (GHD) is not typically 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 the parents.
GH testing may also be performed if there are signs that a child’s body is producing too much of the growth hormone. 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 seven feet or more.
Adult bodies rely on growth hormone to maintain muscle mass and bone density, and to regulate the metabolism of fats. Too little growth hormone can reduce bone density and muscle mass and disrupt fat levels. However, this is very rare. Excess 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 identifies a problem with GH levels. This 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 a person’s age or the nature of the GH abnormality, early detection is very important to increase the chances of a good outcome for the patient.