Growth hormone

Other names: Somatotropin; Human Growth Hormone (HGH); GH

Growth hormone is essential for children’s growth and development; children with a growth hormone deficiency often develop much more slowly than other children and tend to be much smaller. Excessive levels of growth hormone may have the opposite effect and children may grow very quickly and develop very long bones; this can result in gigantism.

When is the test used?

The GH test is not used routinely and is only usually ordered when children show signs of either a growth hormone deficiency or excessive GH production. The test can also be used to check the function of the pituitary gland. The test can also be used on children who have had radiation treatment.

The test may involve either GH suppression or GH stimulation; GH suppression tests are used to test for hyperpituitarism (overactive pituitary gland) and pituitary tumours. GH stimulation tests are used to test for hypopituitarism (underactive pituitary gland).

The test is usually carried out alongside other tests.

The GH test is usually ordered when the child shows symptoms of GH deficiency, icnlduing slow growth, delayed bone development and small stature. The test may also be ordered when tests for hypothyroidism have come back negative and the doctor suspects that the patient has got an underactive pituitary gland.

How is the test performed?

Usually, either a suppression or stimulation test is carried out. For both tests, the patient will be asked to fast for a period of 12 hours before the test; a sample of blood is then taken from a vein in the arm. For the suppression test, the patient will then be given a glucose solution drink and for the stimulation test, the patient will be given an intravenous injection of a solution of either insulin, argenine or GHRH. More blood samples are then taken at timed intervals.

What do the test results show?

If the levels of GH stay higher than they should during the suppression test, this usually indicates that the patient is producing too much growth hormone; patients usually have symptoms of rapid growth and even gigantism.

If levels stay lower than they should during the stimulation test, this usually indicates that the patient has growth hormone deficiency; they will usually have symptoms including slow development and small stature.

Certain types of medication and other health conditions, including pituitary tumours and Cushing’s syndrome, can affect the production of growth hormone.

Specific Blood Tests

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