This information explains growth hormone (GH) stimulation testing using L-arginine (L-AR-jah-neen) and clonidine (KLON-uh-deen) at Memorial Sloan Kettering (MSK), including how to prepare and what to expect after.
For the rest of this resource, our use of the words “you” and “your” refers to you or your child.
About Growth Hormone
Growth hormone (GH) is a hormone made by your pituitary gland, which is a small gland in your brain. Your pituitary gland releases GH into your bloodstream.
GH’s main job is to help children and teenagers grow to their full height. GH works with other hormones, along with exercise, proper nutrition, and rest, to help children and teenagers grow.
GH also affects:
- How well your heart and blood vessels work
- How your body uses fat, makes muscle, and strengthens bones
- Your moods and emotions
- Your overall health
If your body isn’t making enough GH on its own, you can take a medication to replace it.
GH deficiency is when you don’t have enough GH. It’s usually caused by damage to your pituitary gland. This damage can be caused by:
- Cancer treatments, such as radiation or surgery to your head or brain
- A tumor in or near your pituitary gland
GH deficiency can be total or partial. With total GH deficiency, no GH is made. With partial GH deficiency, some GH is made, but not enough to support normal growth.Back to top
About GH Stimulation Testing
A GH stimulation test is done to find out if your pituitary gland is releasing the right amount of GH.
During your GH stimulation test, you’ll take medications to make your pituitary gland release GH. The medications that will be used for your GH stimulation testing are L-arginine and clonidine.
Next, your nurse will take blood samples and measure the amount of GH in your blood. Because GH is released in bursts, the level of GH in a single blood sample is likely to be very low. To get the most accurate results, your nurse will take several blood samples over several hours.Back to top
Before Your GH Stimulation Test
Before your GH stimulation test, ask your doctor or nurse which medications you should take the day of your testing.
Starting at midnight the night before your GH stimulation test, do not eat or drink anything except water. This includes hard candy, gum, and flavored water.
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Eating food or drinking anything except water can change your test results.
The Day of Your GH Stimulation Test
If you feel sick or have a temperature of 100.4° F (38° C) or higher, call your doctor’s office. You may need to reschedule your test.
If your doctor or nurse instructed you to take certain medications before your testing, take only those medications with a sip of water. Depending on what medications you take, this may be all, some, or none of your usual medications.
- Wear comfortable clothes. If possible, wear a short-sleeved shirt.
- Bring books, toys or games to use during your test.
- Bring a snack to eat after your test.
Your test will be done in the Pediatric Day Hospital (PDH). The PDH is located in MSK’s main hospital, at 1275 York Avenue. To get to the PDH, take the B elevators to the 9th floor.
Once it has started, your GH stimulation testing will take about 4 hours. Parents are asked to stay with their child during the test.
You should stay in bed during your test, because the medications may cause lightheadedness or dizziness. If you can, go to the bathroom before your testing so you don’t need to move around after it starts. This will lower your risk of falling.
To begin, your nurse will insert an IV (intravenous) line into a vein, usually in your arm or hand. The IV will be used to draw blood samples and give medication. It will be left in place so you won’t need any other needle pricks during the testing.
The schedule of your GH stimulation testing is as follows:
- A blood sample will be drawn before you get any medications.
- Next, L-arginine will be put into your IV over a 30 minute period.
- Blood samples will be drawn 30 minutes, 60 minutes, and 90 minutes after you’re done getting L-arginine.
- Next, about 90 minutes after you’re done getting L-arginine, you will get clonidine. Clonidine is a pill that you will swallow.
- Blood samples will be drawn 30 minutes, 60 minutes, and 90 minutes after you take clonidine.
After the last blood sample is drawn, your nurse will remove your IV line. They will apply pressure to stop any bleeding and put a small bandage (such as a Band-Aid®) over the spot where the needle was.Back to top
After Your GH Stimulation Test
- You can start eating your normal diet right away.
- Drink plenty of liquids for the rest of the day. Aim for 8 (8-ounce) glasses.
- Don’t go to school, play any sports, or exercise for the rest of the day.
Two to 3 days after your testing, your doctor will contact you about the test results and plan for medical care.Back to top
For the first 24 hours after your GH stimulation test, you may:
- Feel dizzy and lightheaded
- Feel sleepy
- Have a dry mouth
- Have dry eyes or blurry vision
- Feel nauseous
For the first 24 hours after your test:
- Stand up slowly after sitting or lying down.
- Be careful when climbing stairs.
- Avoid any activities that require alertness or clear vision, such as playing sports.
Getting a good night’s sleep after your GH stimulation testing can help these side effects go away. If these side effects don’t go away 24 hours after your testing, call your doctor’s office.
If you have any questions or concerns, talk with a member of the Pediatric Long Term Follow-Up Team. You can reach them Monday through Friday from 9:00 am to 5:00 pm at 212-639-8138. If you have an emergency after 5:00 pm, during the weekend, or on a holiday, please call 212-639-2000.