A growth hormone (GH) test measures the amount of human growth hormone (GH) in the blood. GH is made by the pituitary gland and is needed for growth. It plays an important role in how the body uses food for energy (metabolism). The amount of GH in the blood changes during the day and is affected by exercise, sleep, emotional stress, and diet.
Too much GH during childhood can cause a child to grow taller than normal (gigantism). Too little GH during childhood can cause a child to grow less than normal (dwarfism). Both conditions can be treated if found early.
In adults, too much GH is caused by a non-cancerous tumour of the pituitary gland (adenoma). Too much GH can cause bones of the face, jaw, hands, and feet to grow larger than normal (acromegaly).
Growth hormone can cause the release of other substances (factors) that affect growth and metabolism. One of these is insulin-like growth factor 1 (IGF-1). When the GH level is very high, the IGF-1 level is also very high. A test for IGF-1 may also be done.
Why It Is Done
A test for growth hormone (GH) is done to:
See whether a child whose growth is abnormal has dwarfism or gigantism.
See whether an adult has too much GH (acromegaly) or too little GH.
Check treatment that uses growth hormone.
How To Prepare
In general, there's nothing you have to do before this test, unless your doctor tells you to.
How It Is Done
Blood levels of growth hormone (GH) can change quickly, so more than one blood sample may be taken on different days. Insulin-like growth factor 1 (IGF-1) levels change more slowly, and it may be the first test done.
A health professional uses a needle to take a blood sample, usually from the arm.
How It Feels
When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.
There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.
Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.
High GH values may mean gigantism or acromegaly is present. These conditions are caused by a non-cancerous tumour in the pituitary gland (adenoma). Insulin-like growth factor 1 (IGF-1) levels should also be high.
High GH levels may also be caused by diabetes, kidney disease, or starvation. These conditions do not cause high IGF-1 levels.
Medical Review:Kathleen Romito MD - Family Medicine & E. Gregory Thompson MD - Internal Medicine & Alan C. Dalkin MD - Endocrinology
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