What Is a Growth Hormone Test?

Our bodies usually change quietly, almost without notice. Children grow taller. Our hair often thins as we age. It’s all part of maturing, and it’s controlled by hormones. But sometimes things go wrong.

The hormone that helps control growth and the chemical reactions in our bodies is called human growth hormone. (You may see it written as HGH, or GH for short.) Your body might make it in great amounts or not at all.

Too much or too little HGH can lead to a variety of issues, including:

If you or your child has any of these conditions, your doctor may suggest you take a growth hormone test. The basis of this test is a simple blood sample, which is then looked at in a lab.

Though growth hormone issues can cause problems if left untreated, treating them may be as simple as a regular injection of growth hormone. And in children, these issues may get better on their own over time.

Your Pituitary Gland

Growth hormone is made by the pituitary gland. It’s a pea-sized gland near the center of your head, just below the front of the brain and behind your nose.

GH isn’t the only hormone made by the pituitary gland. In fact, the pituitary has been called the “master gland” because its hormones help control other hormones. It’s part of what’s called the endocrine system, which oversees many body functions.

But if too much or too little GH is in your body, there may be something wrong with your pituitary gland.

In children, you may find this out during a visit with your pediatrician.

During a typical visit, your pediatrician will likely check your child for height, weight, and head size and see how he compares with the normal range for children of that age. If the measurements are outside that range, she may order tests.

If you’re an adult, you may want to visit your doctor if your symptoms include:

  • Low energy
  • Less strength
  • Depression
  • Decline in muscle mass
  • Increase in body fat

These may signal issues with GH production. A test can measure the amount of GH in your blood.

Your pituitary gland releases GH in pulses that vary by sex, age, and even time of day. That is why doctors use different methods to stimulate or suppress the release of growth hormone before you take the test.

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How to Prepare Your Child for the Test

The main GH test for your child is done with two medications that should raise the amount of GH released by his body so that your doctor can test how much his body is making. Doctors call it the “arginine/clonidine stimulation test,” after the two medicines used.

There are a number of things that are required and helpful before your child takes the test:

Fast: Your child shouldn’t have any food after midnight the day of the test.

Avoid medications: He shouldn't take medications the night before and the day of the test unless your doctor or nurse has permitted them. Also, clonidine doesn’t mix with medications such as amphetamine and dextroamphetamine (Adderall) or methylphenidate (Ritalin), so your doctor will give you instructions on whether you need to make any changes with them before the test.

Be ready to pass the time: Since the test takes a few hours, bring books, videos, or other distractions to keep your child from getting bored. Be sure he wears comfortable clothes.

How Adults Can Prepare

Your doctor may ask you to take more than one kind of test.

Besides the stimulation test, you may get:

  • The GH suppression test, which lowers the amount of GH
  • The IGF-1 test, which checks the amount of a different but related hormone
  • Tests to check for issues with other hormones, including cortisol, prolactin, and testosterone.

In some cases, children might also get some of these tests.

As with children, you’ll need to:

Fast: Some medical experts recommend up to 12 hours without food before the test. Talk to your doctor about this beforehand to find out what you should do in your case.

Avoid medications: These include insulin, birth control pills, and the herb St. John’s wort. If you have diabetes, talk with your doctor about your insulin routine.

Don’t exercise: Workouts 10 hours or less before the test can throw off resting hormone levels.

Testing takes up to 3 hours, so you should also dress comfortably and bring a book or some entertainment.

Low blood sugar and obesity may skew results, so talk with your doctor if you have these conditions.

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What Happens During the Test?

For your child, the test begins with a technician placing an IV line in his arm or hand.

After giving a blood sample, your child will take a dose of clonidine by mouth. It comes in either tablet or liquid form. (Clonidine may have side effects -- including lower blood pressure and fatigue -- but it is generally safe for use).

About midway through the test -- maybe 90 minutes in -- your child will get arginine through the IV line.

During all of this, the assistant will probably take a blood sample around every 30 minutes. The samples are not large -- perhaps a couple of teaspoons, total, over the course of the day.

At the end of the test, your child can eat. He should rest afterwards.

It’s a similar process for adults who get the GH stimulation test. Both children and adult blood samples can also be checked for IGF-1 alongside the stimulation test.

If you take the GH suppression test, you’ll drink a glucose solution in the first 5 minutes, and get your blood checked every 30 minutes for 2 hours.

Growth hormone tests aren’t likely to cause any complications, though some people may feel faint. Bruising is possible where the IV line went into your vein.

What the Results Mean

Test results should be ready in several days.

High levels of GH may suggest:

  • Possible acromegaly
  • Gigantism (in children, it can cause really long bones, delayed puberty, and other problems)
  • A tumor

Low levels may indicate:

  • Possible dwarfism
  • Slow growth
  • Hypopituitarism, which means your pituitary gland isn’t working as well as it should.

Normal levels of GH for men are between 1 and 9 nanograms per milliliter (ng/mL). For females, the normal range is 1-16 ng/mL

Because GH issues may be related to other glands, such as the thyroid, your doctor may recommend that you get more tests. If your doctor suspects a tumor, she may ask you to get an MRI, CT scan, or X-ray.

WebMD Medical Reference

Sources

SOURCES:

Lab Tests Online (labtestsonline.org): “Growth Hormone.”
University of Michigan Health System Department of Internal Medicine: “Growth Hormone Disorders.”

The Pituitary Foundation: “What is the pituitary gland?”

American Cancer Society: “What are pituitary tumors?”

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