Growth hormone

Definition

Growth hormone test measures the amount of the growth hormone in blood.

Alternative Names

Why the Test is Performed

Growth hormone may be measured when there is abnormal growth in adults and children or when there is a history of a pituitary problem.

Growth hormone is released from the anterior pituitary gland. Pituitary adenomas can produce excess growth hormone. This can cause abnormal growth patterns called acromegaly in adults and gigantism in children. Excess growth hormone can increase blood pressure and blood sugar.

Individuals with growth hormone resistance or known pituitary disease may not produce enough growth hormone. In children this can cause short stature. In adults, growth hormone insufficiency can lead to changes in muscle mass, cholesterol levels, and bone strength.

How the Test is Performed

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. An elastic band is placed around the upper arm to apply pressure and cause the vein to swell with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

For infants or young children, the area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. A bandage may be applied to the puncture site if there is any bleeding.

How to Prepare for the Test

There is no special preparation.

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.

Risks

• Excessive bleeding
• Fainting or feeling lightheaded
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)
• Multiple punctures to locate veins

Considerations

Growth hormone measurements are usually combined with other laboratory tests, such as IGF-1 levels or provocative tests, such as GHRH stimulation tests. Due to considerable variation in growth hormone levels over the course of a day, the test is often repeated several times to get a better picture of average levels.

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.

Normal Results

The normal range is 0 to 3 ng/ml. Normal value ranges may vary slightly among different laboratories.

Note: ng/ml = nanograms per milliliter

What Abnormal Results Mean

High levels of growth hormone may indicate

• Acromegaly
• Giantism
• Pituitary tumor
• Growth hormone resistance

Low levels of growth hormone may indicate:

• Dwarfism
• Hypopituitarism