IGF-1 (Insulin-like Growth Factor 1) Test
Reviewed
Also called: Somatomedin C test, IGF-1 test
This test measures the amount of IGF-1 (insulin-like growth factor 1) in your blood. IGF-1 manages the effects of growth hormone (GH) in your body.
Specimen: Blood
Why this test may be ordered
- To evaluate symptoms of growth hormone disorders in children (e.g., slowed growth, short stature) or adults (e.g., fatigue, low bone density, enlarged hands/feet, coarse facial features).
- To monitor treatment for known growth hormone disorders.
Preparation and collection
You don't need any special preparations for an IGF-1 test.
A health care professional will take a blood sample from a vein in your arm, using a small needle. This usually takes less than five minutes.
There is very little risk to you or your child in having a blood test. There may be slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
Understanding results
Levels of IGF-1 and GH change throughout your life. But IGF-1 levels are more stable.
- Lower than normal IGF-1 level: If your child's results show lower than normal levels of IGF-1, it probably means they have a GH deficiency or insensitivity to GH. Limitation: If your results show lower than normal IGF-1, it may be due to a normal age-related decrease in the hormone or other conditions. Next step: Your provider may order more tests to help make a diagnosis.
- Higher than normal IGF-1 level: Higher than normal levels of IGF-1 may mean gigantism in children or acromegaly in adults. Limitation: But if the cause is not a tumor, you or your child may need more tests to identify the cause. Next step: Treatment for the tumor may include radiation therapy, surgery, and/or medicines.
- IGF-1 levels change normally with age (low in childhood, peak during puberty, decrease in adulthood).
- Lower than normal levels may be due to growth hormone deficiency, growth hormone insensitivity, or normal age-related decline.
- Higher than normal levels may indicate gigantism (children) or acromegaly (adults), often from a pituitary tumor.
- Interpretation requires correlation with clinical findings and additional tests (e.g., GH stimulation/suppression test, IGFBP-3 test).
What to do next
Your provider may order growth hormone tests to help diagnose a GH disorder. Your provider may order more tests to help make a diagnosis.
- What are the symptoms that led to ordering this test?
- What is my age and how does it affect the interpretation?
- Will I need additional tests to confirm the diagnosis?
- What treatment options are available if the results are abnormal?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.
U.S. National Library of Medicine: IGF-1 (Insulin-like Growth Factor 1) Test