IGF-1 Hormone: Testing, Ranges, and What They Mean

What Is IGF-1?

IGF-1, or Insulin-like Growth Factor-1, is a hormone that plays a key role in growth and development. It is mainly produced by the liver after stimulation by growth hormone (GH). IGF-1 helps cells grow, repair, and function properly. While it is most important during childhood and adolescence, it also supports tissue health throughout life.

In the body, IGF-1 acts as a messenger for GH. Growth hormone levels can vary a lot during the day, but IGF-1 stays more stable. This stability makes IGF-1 a reliable biomarker for checking how much GH your body produces over time.

Doctors use IGF-1 levels to help diagnose conditions related to abnormal growth hormone activity. High levels can be linked to conditions like acromegaly or gigantism. Low levels can point to growth hormone deficiency or problems with the body’s ability to respond to it. By measuring IGF-1, healthcare providers can get a clearer picture of how well your growth system is working.

When Is IGF-1 Testing Recommended?

IGF-1 testing helps doctors evaluate how growth hormone is affecting your body. The test may be recommended in the following situations:

• Signs of too much growth hormone: Such as enlarged hands, feet, or facial features, which may suggest acromegaly or gigantism.
• Signs of too little growth hormone: Including slow growth in children or reduced muscle mass and energy in adults.
• Monitoring growth hormone treatment: To check if the therapy is working effectively.
• Suspicion of growth hormone insensitivity: When the body cannot use GH properly, as in certain rare genetic conditions.
• Follow-up after treatment for GH-related disorders: To see if hormone levels have returned to normal.

How Is IGF-1 Testing Conducted?

IGF-1 is measured through a blood test. A small sample is taken from a vein in your arm. Because IGF-1 remains relatively stable throughout the day, the timing of the test is less critical compared to GH testing.

The test is often ordered as part of a broader evaluation for growth disorders. It can be combined with other hormone tests, such as growth hormone stimulation or suppression tests, to confirm a diagnosis.

Preparation for the test is usually simple. In most cases, you can eat and drink normally beforehand, unless your doctor advises otherwise. However, some tests that are done together with IGF-1 may require fasting, so always follow your healthcare provider’s instructions.

What Are the Normal IGF-1 Levels?

Normal IGF-1 levels depend on your age, sex, and stage of life. Children and teenagers naturally have higher levels because their bodies are still growing. Levels usually peak during adolescence and then gradually decrease with age.

• Children (0-5 years): 2-24 nmol/L
• Older children (6-10 years): 8-40 nmol/L
• Teens (11-20 years): 12-66 nmol/L
• Adults (21-50 years): 10-49 nmol/L
• Older adults (51+ years): 7-29 nmol/L

Note: The units of measurement and the normal ranges can differ depending on the laboratory and the specific methods used.

What Do Abnormal Levels Mean?

IGF-1 High Levels

High IGF-1 levels usually indicate that the body is producing too much growth hormone. This can happen due to medical conditions or other factors. Possible causes include:

• Acromegaly - A condition in adults where excess GH causes enlarged bones and soft tissues, often from a pituitary tumor.
• Gigantism - Similar to acromegaly but occurring in children and teens before growth plates close, leading to excessive height.
• Pituitary tumors - Noncancerous growths that produce extra growth hormone.
• Excessive GH therapy - Overuse of growth hormone treatment can raise IGF-1 beyond normal limits.
• Pregnancy - Naturally increases IGF-1 levels due to hormonal changes.

If you have high IGF-1 levels:

• Follow up with your doctor for further tests, such as imaging of the pituitary gland.
• Discuss possible adjustments to any hormone treatments you are receiving.
• Monitor symptoms like joint pain, changes in appearance, or headaches.
• Maintain a balanced diet and avoid unapproved hormone supplements.
• Attend regular check-ups to track hormone levels over time.

IGF-1 Low Levels

Low IGF-1 levels often suggest the body is not producing enough growth hormone, or that it is not responding to GH properly. Possible causes include:

• Growth hormone deficiency - Can be present from birth or develop later in life, affecting growth and metabolism.
• Laron syndrome - A rare genetic condition where the body cannot use growth hormone effectively.
• Pituitary damage - Injury, surgery, or radiation affecting GH production.
• Chronic illnesses - Certain long-term health problems can reduce IGF-1 production.
• Severe malnutrition - Lack of nutrients needed for hormone production.

If you have low IGF-1 levels:

• See an endocrinologist for further evaluation.
• Ensure you are eating enough nutrient-rich foods to support hormone production.
• Treat any underlying chronic conditions that may be affecting your hormone levels.
• Follow your healthcare provider’s plan for regular testing.
• Focus on healthy lifestyle habits, such as regular exercise and good sleep, to support overall hormone health.

Which Specialist Should You Consult?

If your IGF-1 levels are abnormal, the best specialist to see is an endocrinologist. Endocrinologists focus on hormone-related conditions and can determine the cause of abnormal levels. In some cases, your primary care doctor may refer you to other specialists, such as a neurosurgeon if a pituitary tumor is suspected.