Patient education: Growth hormone testing (The Basics)

What is growth hormone testing? — 

This means blood tests to measure the level of growth hormone, or "GH," in the blood.

GH is a substance made by a gland located at the base of the brain, called the "pituitary gland." Children need GH to grow taller and develop muscles. Adults need GH for their body to work normally.

The level of GH in your blood normally goes up and down throughout the day. It is also affected by things like exercise, sleep, and certain medicines. For this reason, a single blood test cannot give your doctor enough information about your GH level. Instead, they will measure your GH level after giving you a sugary drink or a medicine that affects your GH levels. The medicine might be given by mouth, as a shot, or through a thin tube that goes into a vein (called an "IV").

Having too much or too little GH can lead to health problems. Having too little GH is called "GH deficiency." Having too much is called "GH excess."

Why might I get GH testing? — 

Doctors might do GH testing if:

●They suspect a person has too little GH:

•In adults, the most common cause is a tumor in the pituitary gland.

•Children can be born with too little GH. If a child is not growing normally, doctors can do different tests to figure out the cause.

●They suspect a person has too much GH:

•In adults, a tumor in the pituitary gland can cause some parts of the body to grow bigger than normal over time. This condition is called "acromegaly."

•In children, too much GH cause very fast growth.

Often, other tests are done first, then GH testing is done to confirm a diagnosis.

How do I prepare for GH testing? — 

You need to go to a doctor's office or hospital for the test. Your doctor or nurse will tell you where to go for this. Depending on how the testing will be done, they might also ask you to:

●Not eat or drink anything for 8 to 12 hours before the test

●Stop taking certain medicines before the test

The test involves a "blood draw" to get a sample of blood for testing. Tell the staff:

●If you take "blood thinner" medicines or have a bleeding problem – They will make sure your bleeding is under control before you leave.

●If you have a latex allergy – Some of the supplies used for blood draws might contain latex.

●If you have a preferred arm to use for the blood draw

What happens during GH testing? — 

The process depends on the reason for testing.

To check for GH deficiency:

●You will get a medicine to cause your body to try to make GH. This might be given by mouth, as a shot, or through an IV.

●The staff will do a blood draw (figure 1) and test your blood. They will do this several more times over a few hours.

To check for GH excess:

●You will get a blood draw to measure your GH level.

●Then, you will drink a special drink with a lot of sugar. Normally, this causes the GH level to decrease.

●You will get another blood test about 2 hours later. This to check if your GH level has changed.

Most of the time, getting blood taken does not cause problems. You might have a little soreness or bruising where the needle went in.

What do my results mean? — 

Your doctor or nurse will tell you when to expect your results, and will contact you with the results. Or if you use an online "patient portal," you might get an alert there when your results are ready.

If the test shows your GH level is abnormal, your doctor or nurse will talk to you about what to do next. They might need to do more tests to figure out the cause.

If you do have a health problem, your doctor will work with you to come up with a treatment plan.

More on this topic

Patient education: My child is short (The Basics)
Patient education: Growth hormone treatment in adults (The Basics)
Patient education: Pituitary adenoma (The Basics)
Patient education: Acromegaly (The Basics)

Patient education: Acromegaly (Beyond the Basics)