What Should You and Your Child Expect at a Growth Hormone Stimulation test?
Pediatric endocrinologists will ask their nurses to perform a growth hormone stimulation test in order to identify whether growth hormone deficiency is the reason for poor growth or short stature in a child. A single blood sample from a child is not enough to determine whether a child has growth hormone deficiency because growth hormone is released into the blood from the pituitary gland irregularly in response to normal activities like sleep, after eating meals, exercise or even in response to some medications.
Your child's endocrinologist may suggest that they fast before the test by not eating breakfast or drinking any water on the morning of. On the day of the test, you and your child will be brought into the testing room where growth hormone stimulation tests are conducted. Then your child will have medicated cream placed on their arm where the IV will go. The cream numbs the arm so when the IV begins your child will be unable to feel it. The IV contains a local anesthetic called lidocaine. In the testing room there is a TV, where your child's favorite video can be played.
The doctor will then ask you questions about your child's health and then conduct a brief physical examination of your child to make sure your child is healthy. The nurse will take your child's blood pressure both before and during the course of this test to ensure it is staying in a good range. The nurse will start the IV as soon as the arm is numb and then a blood sample will be drawn. In some scenarios other blood samples will be taken before the test starts depending on your child's need for other laboratory tests.
Next, the nurse will give your child the medication(s) chosen by your child's pediatric endocrinologist. The four types of medications typically used during these tests are Arginine, L-Dopa, Clonidine, and Propranolol or Glucagon. These medications are given through the IV or in crushed pill form mixed with flavoring for your child's comfort. Often, Arginine and Clonidine are given together, or Clonidine and L-dopa are given together. Propranolol is sometimes added. Glucagon can be given with arginine or one of the other medications. As many as 4-6 blood samples will be obtained from the IV for about two hours. Each blood sample taken will only be about a teaspoon of blood.
Dr. Lynne Levitsky assures that a pediatric endocrinologists, nurses and other personal will always be there to supervise the entire test. When the test is completed, the IV will be removed and a bandage will be placed on the area. Once your child is awake and feeling well, you can take them home. Your child's endocrinologist will discuss some of the minor side effects that the medicine may cause. They can eat whatever they wish after and there should be no long term effects from this test. Your child's endocrinologist and other experts at Mass General for Children will review the test results and determine the best treatment option. You will be contacted within a week of the test by your child's endocrinologist to schedule a time to meet and discuss the next steps for your child.
What Type of Medication Will My Child Be Given During a Growth Hormone Stimulation Test?
Your child's Pediatric Endocrinologist will determine which medication is best for your child and then explain to you why that choice was made. Some of the options include:
- Arginine, which is an amino acid that will help stimulate the release of growth hormone into the body. Arginine is found our blood and also in many foods like milk. It will be given to your child through an IV into their vein.
- Glucagon is a hormone that raises blood sugar and is made by the pancreas of the body. It also can cause growth hormone to be released into the blood. Some side effects of this medication include nausea, stomach pain and vomitting, all usually about an hour or so after the injection. Despite these side effects, glucagon is a very strong stimulator of growth hormone release, and there are times when it is important to use this hormone to see if a child is missing growth hormone.
- L-Dopa (Carbidopa) is a medication in pill form that is often given to patients with Parkinson's disease. A single does will be given to your child to stimulate growth hormone. Some side effects from this medication include nausea or vomiting for as short as an hour.
- Clonidine is a medication in pill form that is often used to help patients sleep or lower blood pressure. Children often fall asleep after getting the clonidine pill and will wake up at the end of the test. Some children's blood pressure will lower during this test but will return to normal after the test. Since they are lying down during the test, it will not bother them.
- Propranolol is another pill form medication that is also used to treat high blood pressure. Most children do not experience any side effects. This medication may cause children with asthma to wheeze, which is why children with asthma are not normally given this medication. If a child develops a low blood pressure during this test with this medication, it will go away as the mediation wears off within a few hours.
All of these potential and rare side effects are temporary and should pass quickly. Your child's endocrinologist will discuss with you in further detail about the minor and uncommon side effects to these medications.