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Insulin-like Growth Factor 1 (IGF-1) Test

The Insulin-like Growth Factor 1 (IGF-1) test is a blood test used to measure the level of IGF-1 in the blood. IGF-1 is a protein that plays a crucial role in cell growth and development.

What is IGF-1?

IGF-1, also known as somatomedin C, is a hormone produced primarily by the liver in response to growth hormone (GH) stimulation. It helps regulate cell growth, differentiation, and survival. IGF-1 levels typically peak during puberty and decline with age.

Purpose of the Test

The IGF-1 test is used to:

  • Diagnose and monitor growth hormone-related disorders, such as acromegaly (excess GH production) or growth hormone deficiency
  • Evaluate short stature or growth retardation in children
  • Monitor the effectiveness of growth hormone therapy
  • Investigate conditions associated with abnormal IGF-1 levels, such as Laron syndrome (a rare genetic disorder characterized by GH insensitivity)

How is the Test Performed?

The IGF-1 test involves a blood draw, typically from a vein in the arm. The blood sample is then sent to a laboratory for analysis.

Interpretation of Results

IGF-1 levels are usually measured in nanograms per milliliter (ng/mL) or micrograms per liter (μg/L). Reference ranges may vary depending on the laboratory and the individual's age, sex, and other factors. Abnormal IGF-1 levels can indicate:

  • High levels: Acromegaly, gigantism, or other conditions associated with excess GH production
  • Low levels: Growth hormone deficiency, Laron syndrome, or other conditions associated with impaired GH function

Limitations and Considerations

The IGF-1 test has some limitations:

  • IGF-1 levels can be influenced by factors such as nutrition, sleep, and certain medications
  • Reference ranges may vary depending on the laboratory and individual characteristics
  • A single IGF-1 measurement may not accurately reflect GH function or diagnose a specific condition; multiple measurements and other diagnostic tests may be necessary

Clinical Significance

The IGF-1 test is an important tool in the diagnosis and management of growth hormone-related disorders. Abnormal IGF-1 levels can have significant clinical implications, including:

  • Growth retardation or excess growth
  • Increased risk of certain health conditions, such as diabetes, cardiovascular disease, or osteoporosis
  • Necessity for growth hormone therapy or other treatments to regulate GH function

Article last updated on: 15th June 2025.
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