The growth hormone (GH) blood test determines the levels of growth hormone in the blood. If they are low the treatment is prescribed.
The growth hormone (GH) stimulation test measures the ability of the body to produce GH.
How is the test performed?
Blood is drawn several times. Blood samples are taken through an intravenous (IV) line instead of reinserting the needle each time. The test takes between 2 and 5 hours.
The procedure is done the following way:
- An IV is usually placed in a vein, most often the inside of the elbow or the back of the hand. The site is first cleaned with germ-killing medicine (antiseptic).
- The first sample is drawn early in the morning.
- Medication is given through the vein. This medicine stimulates the pituitary gland to release GH. Several medicines are available. The health care provider will decide which medication is best.
- Additional blood samples are drawn over the next few hours.
- After the last sample is taken, the IV line is removed. The pressure is applied to stop any bleeding.
What are the types of HGH testing?
There are a few variants of human growth hormone testing:
- GH serum test
- Insulin-like growth factor-1 test
- GH suppression test
- GH stimulation test
1. An HGH Serum Test is ordered to assess pituitary function and help diagnose conditions resulting from the deficiency or overproduction of the human growth hormone (HGH) such as hypothalamic disorder, hypopituitarism, acromegaly, and ectopic growth hormone production by neoplasm. The test measures the amount of growth hormone in the blood.
The HGH Serum Test is also commonly referred to as simply GH, HGH, or human growth hormone, as well as Somatotropic hormone, Somatropin, or STH. To prepare for this blood test, patients are asked to fast for 10-12 hours and rest for at least 30 minutes prior to collection. Test results will be available within 2-3 days. Insurance is not required to order this test. Patients also do not need a doctor’s order.
The HGH Serum Test is often ordered along with an IGF-1 Blood Test. Since HGH is secreted in pulses throughout the day, a single test may not accurately show a deficiency or excess. Insulin-like growth factor (IGF) mirrors GH, but IGF is stable throughout the day, and as a result, may be a more accurate indicator of average GH levels.
2. Insulin-like growth factor-1 (IGF-1) is a hormone that, along with growth hormone (GH), helps promote normal bone and tissue growth and development. The test measures the amount of IGF-1 in the blood.
IGF-1 is primarily produced in the liver, skeletal muscles, and many other tissues in response to GH stimulation. IGF-1 mediates many of the actions of GH, stimulates the growth of bones and other tissues, and promotes the production of lean muscle mass. IGF-1 also plays a role in non-growth activities, such as glucose and lipid metabolism, and has been implicated in metabolic syndrome.
Since GH is released into the blood in pulses throughout the day, it is difficult to interpret the results from a single GH test. IGF-1 mirrors GH excesses and deficiencies, but unlike GH, its level is stable throughout the day. This makes IGF-1 a useful indicator of average GH levels. The IGF-1 test is therefore often used to help evaluate for GH deficiency or GH excess.
3. The growth hormone suppression test determines whether growth hormone (GH) production is being suppressed by high blood sugar.
At least three blood samples are taken.
The test is done in the following way:
- The first blood sample is collected between 6 a.m. and 8 a.m. before you eat or drink anything.
- You then drink a solution containing glucose (sugar). You may be told to drink slowly to avoid becoming nauseated. But you must drink the solution within 5 minutes to ensure the test result is accurate.
- The next blood samples are usually collected for 1 to 2 hours after you finish drinking the glucose solution. Sometimes they are taken every 30 or 60 minutes.
- Each sample is sent to the laboratory right away. The lab measures the glucose and GH levels in each sample.
4. Depending on the clinic or facility where you undergo a GH stimulation test, the specific procedure may vary slightly. In general, here’s what you can expect if a doctor orders a GH stimulation test for you or a family member:
A healthcare provider will place an IV (intravenous line) in a vein in your arm or hand. The procedure is similar to a blood test. The major difference is that a small needle connected to a tube that is part of the IV stays in your vein.
You may experience some discomfort when the needle pierces your skin, and some bruising afterward, but the risks and side effects are minimal.
A healthcare provider will take an initial blood sample through the IV. This and all later samples will most likely be collected using the same IV line.
Then you will receive a GH stimulant through the IV. This is a substance that typically encourages an increase in GH production. Some commonly used stimulants are insulin and arginine.
Next, a healthcare provider will take several more blood samples at regular intervals. The entire procedure usually takes about three hours.
After the test, laboratory professionals will analyze your blood samples to see whether your pituitary gland has produced the expected amount of GH in response to the stimulant.
How to prepare for the test?
DO NOT eat for 10 to 12 hours before the test. Eating food can change the test results.
Some medicines can affect the test results. Ask a doctor if you should stop taking any of your drugs before the test.
How the test will feel?
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging sensation. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why the test is performed?
This test is most often done to find out whether a growth hormone deficiency (GH deficiency) is causing current health disorders in adults of middle age.
Normal results include:
- For adult males — 0.4 to 10 nanograms per milliliter (ng/mL), or 18 to 44 picomoles per liter (pmol/L)
- For adult females — 1 to 14 ng/mL, or 44 to 616 pmol/L
- For children — 10 to 50 ng/mL, or 440 to 2200 pmol/L
A normal value rules out HGH deficiency.
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to a doctor about the meaning of your specific test results.
What abnormal results mean?
If this test does not raise GH levels, there is a reduced amount of HGH stored in the anterior pituitary. In adults, it may be linked to adult GH deficiency.
There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight, but may include:
- excessive bleeding;
- multiple punctures to locate veins;
- fainting or feeling lightheaded;
- hematoma (blood accumulating under the skin);
- infection (a slight risk any time the skin is broken).
Medicines that stimulate the pituitary during the test may cause side effects. A doctor can tell you more about this and help you select the most suitable and safest medication just for you.
To get a free consultation and ask any questions about the test or HGH therapy, just get in touch.