Insulin Like Growth Factor 1 Test (IGF1)

Insulin Like Growth Factor 1 Test (IGF1)-Why am I having this test?

Insulin Like Growth Factor 1 Test is used to help diagnose the cause of abnormal patterns of growth or other conditions that cause low levels of growth hormone (GH) in the body.

IGF 1 levels are low when GH levels are low. Therefore, this test can be used to predict GH levels in the body. Also, because IGF1 blood levels are more stable throughout the day than GH blood levels are, the IGF1 test is considered to be a more reliable test.

The IGF1 test may also be done to see how well treatments with GH are working or to check the function of your pituitary gland. The pituitary gland produces GH and many other hormones in your body.

Testing of pituitary gland function may be needed for people with certain signs or symptoms, including:

  • Children with these signs or symptoms:
    • Slow growth or delayed development over a period of time when compared to normal growth expectations.
    • Being shorter than expected for their age, sex, or family history (dwarfism).
    • Being larger in stature and height than expected for their age, sex, or family history (gigantism).
  • Adults with these signs or symptoms:
    • Decreased bone density, decreased muscle strength, and high levels of blood fat (lipids) that are not explained by other factors.
    • Signs of acromegaly, such as having fingers, toes, jaw, ears, and nose grow out of proportion to the rest of the body.

What is being tested?

This test measures the IGF-1 levels in your blood to help determine how much growth hormone your body is producing.

What kind of sample is taken?

A blood sample is required for this test. It is usually collected by inserting a needle into a blood vessel.

How do I prepare for this test?

  • Do not eat or drink anything after midnight on the night before the test or as told by your health care provider.
  • Tell your health care provider if you have had estrogen treatment. This may decrease your IGF-1 levels.

How are the results reported?

Your test results will be reported as ranges. Your health care provider will compare your results to normal ranges that were established after testing a large group of people (reference ranges). Reference ranges may vary among labs and hospitals. For this test, common reference ranges are:

  • Adult: 42–110 ng/mL.
  • Child, Female:
    • 0–8 years old: 5–128 ng/mL.
    • 9–10 years old: 24–158 ng/mL.
    • 11–13 years old: 65–226 ng/mL.
    • 14–15 years old: 124–242 ng/mL.
    • 16–17 years old: 94–231 ng/mL.
    • 18–19 years old: 66–186 ng/mL.
  • Child, Male:
    • 0–8 years old: 2–118 ng/mL.
    • 9–10 years old: 15–148 ng/mL.
    • 11–13 years old: 55–216 ng/mL.
    • 14–15 years old: 114–232 ng/mL.
    • 16–17 years old: 84–211 ng/mL.
    • 18–19 years old: 56–177 ng/mL.

What do the results mean?

Results within the reference range are considered normal. A test result that is higher than the reference range may indicate various conditions, such as:

  • Gigantism.
  • Acromegaly.
  • Being exposed to high levels of stress.
  • Recent major surgery.
  • Low blood sugar (hypoglycemia).
  • Starvation.
  • Deep-sleep state at the time of testing.
  • Recent exercise.

A test result that is lower than the reference range may indicate:

  • Abnormally low levels (deficiency) of GH.
  • Abnormally low pituitary gland function.
  • Pituitary tumors.
  • Dwarfism.
  • High blood sugar (hyperglycemia).
  • Failure to thrive.
  • Delayed sexual maturity in adolescents.
  • Malnutrition.
  • Malabsorption of nutrients from the digestive tract.
  • Anorexia nervosa.
  • Severe liver disease.
  • Underactive thyroid gland (hypothyroidism).

Talk with your health care provider about what your results mean.

Questions to ask your health care provider

Ask your health care provider, or the department that is doing the test:

  • When will my results be ready?
  • How will I get my results?
  • What are my treatment options?
  • What other tests do I need?
  • What are my next steps?

Summary

  • The insulin-like growth factor-1 (IGF-1) test is used to help diagnose the cause of abnormal patterns of growth or other conditions that cause low levels of growth hormone (GH) in the body.
  • The IGF-1 test may also be done to see how well treatments with GH are working or to check the function of your pituitary gland.
  • This test measures the IGF-1 levels in your blood to help determine how much growth hormone your body is producing.
  • Talk with your health care provider about what your results mean.
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