Growth hormone testDefinition:
The growth hormone test measures the amount of growth hormone in the blood.
How the test is performed:
Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.
Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.
How to prepare for the test:
Your doctor may give you special instructions about what you can or cannot eat before the test.
How the test will feel:
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the test is performed:
Growth hormone may be measured when adults or children are not growing normally, or when there is a history of a pituitary gland problem.
Growth hormone is released from the anterior pituitary gland. Too much growth hormone can cause abnormal growth patterns called acromegaly in adults and gigantism in children.
Too little growth hormone can cause short stature in children, and changes in muscle mass, cholesterol levels, and bone strength in adults.
The normal range varies by age and laboratory.
GH is released in pulses, so a higher level may be normal if the blood was drawn during a pulse.
Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
What abnormal results mean:
High levels of growth hormone may indicate:
Low levels of growth hormone may indicate:
What the risks are:
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Growth hormone measurements are usually combined with other laboratory tests, such as:
- IGF-1 levels
- GHRH or GHRH-arginine stimulation
- Oral glucose tolerance suppression
Because growth hormone levels can change over the course of a day, the test is often repeated several times to get a better picture of average levels.
Melmed S, Kleinberg D. Anterior pituitary. In: Kronenberg HM, Melmed S, Polonsky KS, Larsen PR, eds. Williams Textbook of Endocrinology. 11th ed. Philadelphia, PA: Saunders Elsevier; 2008: chap 8.