Other names: Somatomedin C

The IGF-1 (the insulin-like growth factor-1) test is an indicator of the amount of growth hormone being produced by the body. IGF-1 and GH (growth hormone) are peptide hormones, which are composed of a series of amino acids; both hormones are essential for growth and development and changes in the levels of hormone produced by the body can contribute to health conditions.

Why is the test used?

The test is primarily used to determine the cause of growth problems or abnormalities; it is also useful for evaluating the function of the pituitary gland.

The test is usually ordered when a child has symptoms of a growth disorder; for example, if they are growing and developing very slowly and is much shorter than average. The test may also be ordered along with a GH suppression test when a child has symptoms of overproduction of growth hormone.

The test may also be ordered if the doctor suspects that the patient has got a tumour on the pituitary tumour.

How is the test performed?

The test is carried out by inserting a needle into a vein in the patient’s arm (usually on the inside of the elbow); the blood is drawn out and collected in a syringe. Once the sample has been collected, it will be bottled, labelled and sent away to the laboratory for analysis.

The test may be carried out alongside other tests, so it may be necessary for the patient to fast for a period of time before the test is done (usually 12 hours overnight).

What do the test results show?

The test results must be considered in context with the patient’s general health and medical history.

Decreased levels of IGF-1 usually indicate a deficiency or sensitivity to GH (growth hormone); however, the decrease may also be caused by reduced function of the pituitary gland. Levels may also be decreased if the patient has an eating disorder or chronic kidney or liver disease.

Increased levels of IGF-1 are usually associated with overproduction of GH (growth hormone); levels usually increase during puberty and pregnancy but elevated levels in children may contribute to symptoms of gigantism. If levels are elevated during adulthood, this is usually due to a pituitary tumour.

If IGF-1 levels are normal but the doctor still suspects a problem, they may order further tests.

Specific Blood Tests

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