Growth Hormone
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- Also Known As:
- GH
- Human Growth Hormone
- HGH
- Somatotropin
- Growth Hormone Stimulation Test
- Growth Hormone Suppression Test

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At a Glance
Why Get Tested?
To help diagnose growth hormone (GH) deficiency or, less commonly, growth hormone excess; to evaluate pituitary function; to monitor the effectiveness of treatment for excess GH
When To Get Tested?
When a child has slow growth, short stature, and delayed motor development or sometimes when an adult has decreased bone density and/or muscle strength and elevated blood lipid levels that could be related to growth hormone deficiency; when a child or adult has signs and symptoms suggestive of growth hormone excess, which can cause two rare conditions, gigantism and acromegaly, respectively; when a pituitary disorder is suspected and other pituitary hormone levels are abnormal
Sample Required?
Usually several blood samples, drawn at timed intervals from veins; sometimes a single sample of blood, drawn following a fast and rest, after a period of strenuous exercise, or after drinking a glucose (sugar) solution
Test Preparation Needed?
Follow any instructions you are given, such as to fast, in order to prepare for this test.
You may be able to find your test results on your laboratory’s website or patient portal. However, you are currently at Testing.com. You may have been directed here by your lab’s website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab’s website or portal, or contact your healthcare practitioner in order to obtain your test results.
Testing.com is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.
The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.
If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.
Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called “normal” values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.
While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are “within normal limits.”
For more information, please read the article Reference Ranges and What They Mean.
What is being tested?
Growth hormone (GH) is a hormone that is essential for normal growth and development in children. It promotes proper linear bone growth from birth through puberty. In both children and adults, growth hormone helps regulate the rate at which the body both produces energy from food (metabolism) and makes lipids, proteins, and glucose (sugar). It also helps regulate the production of red blood cells and muscle mass.
Growth hormone is produced by the pituitary gland, a small gland located at the base of the brain behind the bridge of the nose. It is normally released into the blood in pulses throughout the day and night with peaks that occur mostly during the night. Because of this, a single measurement of the level of GH in blood is difficult to interpret and not usually clinically useful. The value will be higher if the sample is taken during a pulse and lower if it is taken during a period between pulses.
Therefore, procedures called growth hormone stimulation and suppression tests are most often used to diagnose conditions caused by growth hormone deficiency or excess. These procedures are used in conjunction with signs and symptoms and growth factor levels (i.e., insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding protein 3). See “How is the test used?” under Common Questions for more detail.
GH deficiency
Some children have GH deficiency at birth (congenital), but some may develop a deficiency later due, for example, to a brain injury or tumor. These conditions can affect the pituitary gland, causing a decrease in pituitary function, resulting in a lowered production of pituitary hormones (hypopituitarism). Sometimes, the cause of the deficiency is not known, a category referred to as “idiopathic.”
In adults, growth hormone plays a role in regulating bone density, muscle mass, and glucose and lipid metabolism. It can also affect heart and kidney function. Deficiencies may begin in childhood or develop in adulthood. A deficiency can develop, for example, because of damage to the pituitary gland caused by a head injury, brain tumor, or surgery or radiation treatment. This can result in a decrease in pituitary hormones (hypopituitarism).
GH excess
Excess GH is most often due to a pituitary tumor (usually benign) that produces GH.
Too much GH in children can cause their long bones to continue to grow beyond puberty, resulting in the extremely rare condition, gigantism, with heights of 7 feet or more. Those with excess GH may also have thickening of facial features, general weakness, delayed puberty, and headaches. Pituitary tumors releasing excess growth hormone can cause loss of vision if they grow very large.
Excess GH in adults can lead to the rare condition, acromegaly, marked not by bone lengthening but by bone thickening. Although symptoms such as skin thickening, sweating, fatigue, headaches, and joint pain can be subtle at first, increased GH levels can lead to enlarged hands and feet, enlarged facial bones, carpal tunnel syndrome, and abnormally enlarged internal organs. Excess GH can also cause skin tags and intestinal polyps.
Frequently, the pituitary tumor causing the excess can be surgically removed and/or treated with drugs or radiation. In most cases, this will cause GH and IGF-1 levels to return to normal or near normal levels.
If left untreated, both acromegaly and gigantism can lead to complications such as type 2 diabetes, increased risk of cardiovascular disease, high blood pressure, arthritis, and in general, a decreased lifespan.
How is the sample collected for testing?
Growth hormone is released in pulses, so a single measurement of the blood level is not normally clinically useful. Therefore, growth hormone levels are usually measured using growth hormone suppression or stimulation procedures. After fasting for 10 to 12 hours, a blood sample is drawn from a vein in the arm. Then, under medical supervision, the suppression or stimulation procedure is performed. This may involve the use of an intravenous (IV) infusion. Blood samples are then drawn from a vein (or from the IV) at timed intervals.
Sometimes, a single sample of blood is drawn following a fast and rest or after a period of strenuous exercise.
Is any test preparation needed to ensure the quality of the sample?
Follow any instructions you are given. In most cases, you should be fasting. Resting or strenuous exercise for a time period before collection may be required.
Children and pre-teens who are being tested for GH deficiency should be prepared for treatment with sex steroids for a few days prior to testing. Such treatment reduces the number of falsely low GH responses to stimulation. The health practitioner who is ordering the GH testing should provide the child’s parents with a prescription for such medications. Some healthcare practitioners will also prescribe propranolol prior to testing to reduce the number of falsely low GH responses to stimulation.
Common Questions
View Sources
Sources Used in Current Review
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