Growth hormone (HGH) Test

This test is mainly advised to determine the normal pattern of GH secretion or to detect any abnormalities in GH levels- low or high GH.

In addition, it helps asses the functioning of the pituitary gland and is recommended for monitoring the effectiveness of treatment for abnormal GH secretion.

For a random test

• Fasting is needed for eight hours. Drinking water is permitted during this period
• Try to remain in a calm and stress-free environment for 30 minutes prior to the test

For a suppression/stimulation test

• All steroid medications should be discontinued before the test  
• Fasting for 8-10 hours will be required for this test
• The purpose and method of the test will be explained to you

For a random specimen

• Seven millilitres of blood will be collected from a vein in your arm

For a stimulation test

This procedure includes intravenous administration of a drug and withdrawal of several blood samples.

• A baseline blood sample will be collected first
• Depending on the drug administered, further samples will be collected over a period between 30, 60 and 90 minutes after the infusion is completed.

For a suppression test

In place of a drug, an oral glucose solution is administered in this test along with the withdrawal of multiple blood samples.

• First, a technician will collect a baseline blood sample
• Oral glucose solution will then be given
• Blood samples will be collected after 30, 60 and 90 minutes of the procedure depending on the laboratory

Blood samples are carefully labelled stating the time of collection. GH has a half-life of 20 to 25 minutes only so all samples are immediately taken to the laboratory.

Diet and medications can be resumed after the test. Abnormal values should be reported to the primary health care provider or specialist.

Normal results of GH

For a random sample:

Males: Less than 5 nanograms (ng)/mL
Females: Less than 10 milligrams (mg)/mL

For a stimulation test: More than 10 ng/mL

For a suppression test: Less than 2 ng/mL

Abnormal results
For a random specimen, increased values of GH could signify

• Anorexia nervosa
• Acromegaly
• Gigantism
• Hypoglycaemia
• Hypothalamic tumours
• Pituitary tumour
• Starvation
• Surgery
• Sleep

Decreased values are suggestive of

• Failure to thrive
• Dwarfism
• GH deficiency
• Hyperglycaemia
• Hypopituitarism

Stimulation test: A lack of increase in GH suggests GH deficiency.

Suppression test: A slight or no decrease in GH indicates acromegaly.

Factors that may contribute to abnormal values are mentioned below:

• GH values vary with exercise, sleep, nutritional status and stress
• GH should not be tested for at least 48 hours after any radioactive diagnostic tests
• Certain drugs, such as arginine, amphetamines, dopamine, oestrogen, insulin, niacin and oral contraceptives, can increase GH levels
• Drugs, such as antipsychotics, corticosteroids, progestin, valproic acid and dexamethasone, may decrease GH levels

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.