Also Known As
Somatomedin C
Formal Name
Insulin-like Growth Factor - 1
This article was last reviewed on
This article waslast modified on November 5, 2017.
At a Glance
Why Get Tested?

To help diagnose growth hormone (GH) deficiency or, less commonly, growth hormone excess; to evaluate pituitary function; to monitor the effectiveness of GH treatment

When To Get Tested?

When a child has signs and symptoms of slow growth, short stature, and delayed development or an adult has decreased bone density, reduced muscle strength, and increased lipids that suggest insufficient GH and IGF-1 production; when a child or adult has signs and symptoms of gigantism or acromegaly, respectively, that suggest excess GH and IGF-1 production; during and after treatment for GH abnormalities; when a pituitary disorder is suspected

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

Generally none, unless instructed to fast

You may be able to find your test results on your laboratory's website or patient portal. However, you are currently at Lab Tests Online. You may have been directed here by your lab's website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab's website or portal, or contact your healthcare practitioner in order to obtain your test results.

Lab Tests Online is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called "normal" values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."

For more information, please read the article Reference Ranges and What They Mean.

What is being tested?

Insulin-like growth factor-1 (IGF-1) is a hormone that, along with growth hormone (GH), helps promote normal bone and tissue growth and development. The test measures the amount of IGF-1 in the blood.

IGF-1 is produced by the liver and skeletal muscle as well as many other tissues in response to GH stimulation. IGF-1 mediates many of the actions of GH, stimulating the growth of bones and other tissues and promoting the production of lean muscle mass. Since GH is released into the blood in pulses throughout the day, it is difficult to interpret the results from a single GH test. IGF-1 mirrors GH excesses and deficiencies, but unlike GH, its level is stable throughout the day. This makes IGF-1 a useful indicator of average GH levels. The IGF-1 test is therefore often used to help evaluate for GH deficiency or GH excess.

IGF-1 levels, like GH, are normally low in early childhood, increase gradually during childhood, peak during puberty, and then decline in adult life. Deficiencies in GH and IGF-1 may be caused by a dysfunctional pituitary gland with decreased pituitary hormones (hypopituitarism) or by the presence of a non-GH-producing pituitary tumor that damages hormone-producing cells. Deficiencies in IGF-1 also occur where there is a lack of responsiveness to GH. This insensitivity may be primary (genetic) or secondary to conditions such as malnutrition, hypothyroidism, sex hormone deficiency, and chronic diseases. Genetic GH insensitivity (GH resistance) is very rare.

IGF-1 deficiencies early in life, usually the result of GH deficiency, can inhibit bone growth and overall development and can result in a child with a shorter than normal stature. In adults, decreased production can lead to low bone density, less muscle mass, and altered lipid levels. However, testing for IGF-1 deficiency, or GH deficiency, is not routine in adults who have decreased bone density and/or muscle strength or increased lipids. GH deficiency and consequent IGF-1 deficiency is a very rare cause of these disorders.

Excess GH and IGF-1 can cause abnormal growth of the skeleton and other signs and symptoms characteristic of two rare conditions, gigantism and acromegaly. In children, gigantism causes bones to grow longer, resulting in a very tall person with large feet and hands. In adults, acromegaly causes bones to thicken and soft tissues, such as the nose, to swell. Both conditions can lead to enlarged organs, such as the heart, and to other complications such as type 2 diabetes, increased risk of cardiovascular disease, high blood pressure, arthritis, and a decreased lifespan.

The most common reason for the pituitary to secrete excessive amounts of GH is a GH-producing pituitary tumor (usually benign). Frequently, the tumor can be surgically removed and/or treated with drugs or radiation. In most cases, this will cause GH and IGF-1 levels to return to normal or near normal levels.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

In general, no test preparation is needed; however, since this test may be performed at the same time as others, fasting for at least 12 hours may be required.

Accordion Title
Common Questions
  • How is it used?

    A test for insulin-like growth factor-1 (IGF-1) may be used to help:

    • Identify growth hormone (GH) deficiency; it is not diagnostic of a GH deficiency but may be ordered along with GH stimulation tests to offer additional information.
    • As follow-up to abnormal results on other hormone tests
    • Evaluate pituitary function

    Less commonly, IGF-1 tests may be used to detect excess growth hormone and to help diagnose and monitor treatment of two rare conditions, acromegaly and gigantism.

    IGF-1 is a hormone that, along with growth hormone, helps promote normal bone and tissue growth and development. An IGF-1 test is often ordered along with GH. IGF-1 mirrors GH excesses and deficiencies, but the level in the blood is stable throughout the day, making it a useful indicator of average GH levels.

    IGF-1 may be ordered with other pituitary hormone tests, such as prolactin or FSH and LH, to help diagnose pituitary gland dysfunction and decreased pituitary hormones (hypopituitarism).

    IGF-1 testing and a GH suppression test can be used to detect and monitor treatment of a GH-producing pituitary tumor. An anterior pituitary tumor is typically confirmed with imaging scans that help identify and locate the tumor. If surgery is necessary, GH and IGF-1 levels are measured after the tumor's removal to determine whether the entire tumor was successfully removed. Drug and/or radiation therapy may be used in addition to, or sometimes instead of, surgery to try to decrease GH production and return IGF-1 to a normal or near normal concentration. IGF-1 may be ordered to monitor the effectiveness of this therapy at regular intervals for years afterward to monitor GH production and to detect tumor recurrence.

    IGF-1 levels and the measurement of GH can also provide information related to GH insensitivity. Prior to performing definitive GH testing, if the IGF-1 level is found to be normal for age and sex, GH deficiency is excluded and definitive testing is not necessary.

  • When is it ordered?

    IGF-1 testing may be ordered, along with a GH stimulation test, when:

    • A child has symptoms of GH deficiency, such as a slowed growth rate and short stature
    • Adults have symptoms that a health practitioner suspects may be due to a GH deficiency, such as decreased bone density, fatigue, adverse changes to lipid levels, and reduced exercise tolerance. However, testing for IGF-1 deficiency is not routine in adults who have these symptoms; GH and IGF-1 deficiency are only very rare causes of these disorders.

    An IGF-1 also may be ordered when a health practitioner suspects that someone has an underactive pituitary gland and at intervals to monitor those on GH therapy.

    Less commonly, IGF-1 testing may be ordered, along with a GH suppression test, when a child has symptoms of gigantism or when an adult shows signs of acromegaly.

    When a GH-producing pituitary tumor is found, GH and IGF-1 are ordered after the tumor is surgically removed to determine whether all of the tumor has been extracted. IGF-1 also is ordered at regular intervals when someone is undergoing the drug and/or radiation therapy that frequently follow tumor surgery.

    IGF-1 levels may be ordered at regular intervals for many years to monitor a person's GH production and to watch for pituitary tumor recurrence.

  • What does the test result mean?

    A normal level of IGF-1 must be considered in context. Some people can have a GH deficiency and still have a normal IGF-1 level.

    Decreased IGF-1
    If the IGF-1 level is decreased, then it is likely that there is a GH deficiency or an insensitivity to GH. If this is in a child, the GH deficiency may have already caused short stature and delayed development and may be treated with GH supplementation. Adults will have an age-related decrease in production, but lower than expected levels may reflect a GH deficiency or insensitivity.

    If a decrease in IGF-1 is suspected to be due to a more general decrease in pituitary function (hypopituitarism), then several other endocrine glands and their pituitary regulating hormones will need to be evaluated to decide on appropriate treatment. Reduced pituitary function may be due to inherited defects or can develop as a result of pituitary damage following conditions such as trauma, infections, and inflammation.

    Decreased levels of IGF-1 also may be seen with nutritional deficiencies (including anorexia nervosa), chronic kidney or liver disease, inactive/ineffective forms of GH, and with high doses of estrogen.

    Increased IGF-1
    Elevated levels of IGF-1 usually indicate an increased production of GH. Since GH levels vary throughout the day, IGF-1 levels are a reflection of average GH production, not of the actual amount of GH in the blood at the time that the sample for the IGF-1 measurement was taken. This is accurate up to the point at which the liver's capacity to produce IGF-1 is reached. With severely increased GH production, the IGF-1 level will stabilize at an elevated maximum level.

    Increased levels of GH and IGF-1 are normal during puberty and pregnancy but otherwise are most frequently due to pituitary tumors (usually benign). 

    If IGF-1 is still elevated after the surgical removal of a pituitary tumor, then the surgery may not have been fully effective. Decreasing IGF-1 levels during subsequent drug and/or radiation therapies indicate that the treatment is lowering GH production. If levels of IGF-1 become "normalized," then the person is no longer producing excess amounts of GH. When someone is undergoing long-term monitoring, an increase in IGF-1 levels may indicate a recurrence of the pituitary tumor.

  • Is there anything else I should know?

    If an IGF-1 level is normal and a health practitioner still strongly suspects a GH deficiency, then the healthcare provider may order another test, an IGFBP-3 (insulin-like growth factor binding protein 3), to help confirm the GH deficiency. Almost all IGF-1 in the blood is bound to binding proteins, with IGFBP-3 being the most prevalent form, and IGFBP-3 production is also stimulated by GH.

  • What signs and symptoms are seen with deficient GH and IGF-1?

    In children, the following may indicate GH and/or IGF-1 deficiency:

    • Slowed growth rate in early childhood relative to group norms
    • Shorter stature than others of the same chronological age
    • Delayed puberty
    • X-rays showing delayed bone development

    In adults, abnormally low levels of GH and/or IGF-1 may cause subtle, nonspecific symptoms such as:

    • Decreased bone density
    • Fatigue
    • Adverse lipid changes
    • Reduced exercise tolerance
  • What signs and symptoms are seen with excess GH and IGF-1 production?

    In a child, it is unusual tallness. With an adult, it may be more subtle: a larger nose, thicker lips, a more prominent jaw, or rings and shoes that no longer fit. Other signs and symptoms may include:

    • Deepened, husky voice
    • Enlarged organs (liver, heart, kidneys, and spleen)
    • Enlarged tongue
    • Erectile dysfunction
    • Fatigue
    • Headaches and visual disturbances
    • Joint pain and swelling
    • Menstrual cycle irregularities
    • Muscle weakness
    • Snoring
    • Sweating and body odor
    • Thickening of the skin, skin tags
    • Trapped nerves (Carpal tunnel syndrome)
  • Can this test be done in my doctor's office?
    No, this test requires specialized equipment and training and is not available in every laboratory. Your blood may be sent to a reference laboratory.
  • How long do I have to be monitored?

    As long as you are considered to have abnormal (low or high) GH production or are receiving GH replacement therapy, your IGF-1 will need to be monitored. However, IGF-1 is not routinely measured to monitor GH treatment of GH-deficient children. The best index of the effectiveness of GH treatment of children who are GH-deficient is observation of an increase in their growth rate and their absolute height.

View Sources

Sources Used in Current Review

(© 1995–2014). Insulin-Like Growth Factor 1, Serum. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/35099 through http://www.mayomedicallaboratories.com. Accessed August 2014.

Wisse, B. (Updated 2013 November 7). Gigantism. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/001174.htm through http://www.nlm.nih.gov. Accessed August 2014.

Kaneshiro, N. (Updated 2013 August 22). Short stature. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003271.htm through http://www.nlm.nih.gov. Accessed August 2014.

Diaz-Thomas, A. et. al. (Updated 2014 May 12)). Gigantism and Acromegaly. Medscape Drugs & Diseases [On-line information]. Available online at http://emedicine.medscape.com/article/925446-overview through http://emedicine.medscape.com. Accessed August 2014.

Eledrisi, M. (Updated 2013 October 17). Growth Hormone Deficiency. Medscape Drugs & Diseases [On-line information]. Available online at http://emedicine.medscape.com/article/120767-overview through http://emedicine.medscape.com. Accessed August 2014.

Rosenbloom, A. and Guevara-Aguirre, J. (Updated 2014 January 23). Growth Hormone Resistance. Medscape Drugs & Diseases [On-line information]. Available online at http://emedicine.medscape.com/article/922902-overview through http://emedicine.medscape.com. Accessed August 2014.

Meikle, A. W. (Updated 2014 January). Growth Hormone Deficiency. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/GrowthHormone.html?client_ID=LTD#tabs=0 through http://www.arupconsult.com. Accessed August 2014.

Sources Used in Previous Reviews

Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].

Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby's Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.

Thorner, M. et. al. (2003 September 24). Advanced Strategies for Achieving IGF-I Control in Acromegaly. The Endocrine Society [CME on Medscape]. Available online at http://www.medscape.com/viewprogram/2638_pnt through http://www.medscape.com.

Cromie, W. (1999 April 22). Growth Factor Raises Cancer Risk. Harvard Gazette Archives [On-line article]. Available online at http://www.news.harvard.edu/gazette/1999/04.22/igf1.story.html through http://www.news.harvard.edu.

IGF-1 (Insulin-Like Growth Factor 1). ARUP Guide to Clinical Laboratory Testing. [On-line information]. Available online at http://www.arup-lab.com/guides/clt/tests/clt_al3b.jsp#1349162 through http://www.arup-lab.com.

Growth Hormone (Human Growth Hormone, HGH, Somatotropin). Acromegaly, ARUP Guide to Clinical Laboratory Testing. [On-line information]. Available online at http://www.arup-lab.com/guides/clt/tests/clt_al3b.jsp#1349162 through http://www.arup-lab.com.

(2002 Int J Cancer). Elevated IGF-1 Linked to Risk of Ovarian Cancer in Younger Women. National Cancer Institute, CTEP, From Int J Cancer 101:549-554. [On-line information]. Available online at http://ctep.info.nih.gov/resources/gcig/news102902.html through http://ctep.info.nih.gov.

Mayo Clinic Staff (2003 May 08). Acromegaly. MayoClinic.com [On-line information]. Available online at http://www.mayoclinic.com/invoke.cfm?id=DS00478 through http://www.mayoclinic.com.

(2002 June). Acromegaly. NIDDK, NIH Publication No. 02-3924 [On-line information]. Available online at http://www.niddk.nih.gov/health/endo/pubs/acro/acro.htm through http://www.niddk.nih.gov.

(2002) Acromegaly/ MedlinePlus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000321.htm.

(2004 January 23). Unsportsmanlike behavior. The Washington Times [On-line article]. Available online at http://www.washingtontimes.com/functions/print.php?StoryID=20040122-082812-2585r through http://www.washingtontimes.com.

Kass, L. and Council (2003 October). Chapter Three, Superior Performance. Beyond Therapy: Biotechnology and the Pursuit of Happiness, The President's Council on Bioethics [On-line report]. Available online at http://bioethicsprint.bioethics.gov/reports/beyondtherapy/index.html through http://bioethicsprint.bioethics.gov.

(2003 May 30). Race to develop drug abuse test. BBC News [On-line article]. Available online at http://news.bbc.co.uk/1/hi/health/2946344.stm through http://news.bbc.co.uk.

Acromegaly and Gigantism. Merck Manual Second Home Edition [On-line information]. Available online at http://www.merck.com/mrkshared/mmanual_home2/sec13/ch162/ch162e.jsp through http://www.merck.com.

Clemmons, D. (2004 January 1). The relative roles of growth hormone and IGF-1 in controlling insulin sensitivity. J Clin Invest 113(1): 25-27 [On-line article]. Available online at http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=300772 through http://www.pubmedcentral.nih.gov.

(2003 April 14, Updated). Growth Hormone. Index of the Hypothalamus and Pituitary Gland, Colorado State University Hypertext [On-line information]. Available online at http://arbl.cvmbs.colostate.edu/hbooks/pathphys/endocrine/hypopit/gh.html through http://arbl.cvmbs.colostate.edu.

(2003 February 18, Updated). Growth Hormone and Aging. Index of the Hypothalamus and Pituitary Gland, Colorado State University Hypertext [On-line information]. Available online at http://arbl.cvmbs.colostate.edu/hbooks/pathphys/endocrine/hypopit/ghaging.html through http://arbl.cvmbs.colostate.edu.

Pagana, Kathleen D. & Pagana, Timothy J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 879 880.

Clarke, W. and Dufour, D. R., Editors (2006). Contemporary Practice in Clinical Chemistry. AACC Press, Washington, DC. Grenache, D and Willis, M., Chapter 31, Hypothalamic, Pituitary, and Gonadal Disorders. Pp 351-363.

Wu, A. (2006). Tietz Clinical Guide to Laboratory Tests, Fourth Edition. Saunders Elsevier, St. Louis, Missouri. Pp 626-628.

Sheppard, M. (2007 April 3). Growth Hormone Assay Standardization: An Important Clinical Advance. Medscape from Clin Endocrinol. 2007;66(2):157-161. [On-line information]. Available online at http://www.medscape.com/viewarticle/553885 through http://www.medscape.com. Accessed 8/18/07.

(2007 April). Acromegaly. NIDDK, NIH Publication No. 02-3924 [On-line information]. Available online at http://www.niddk.nih.gov/health/endo/pubs/acro/acro.htm through http://www.niddk.nih.gov. Accessed September 2007.

William E. Winter, MD, FACB. Lab Tests Online adjunct board member.

(© 1995-2010). Unit Code 15867: Insulin-Like Growth Factor 1 (IGF-1), Serum. Mayo Clinic, Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/15867 through http://www.mayomedicallaboratories.com. Accessed October 2010.

Meikle, W. and Roberts, W. (Updated 2010 May). Growth Hormone Deficiency. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/GrowthHormone.html?client_ID=LTD through http://www.arupconsult.com. Accessed October 2010.

Kemp, S. (Updated 2010 May 5). Growth Hormone Deficiency. eMedicine [On-line information]. Available online at http://emedicine.medscape.com/article/923688-overview through http://emedicine.medscape.com. Accessed October 2010.

(2008 May). Acromegaly. National Endocrine and Metabolic Diseases Information Service [On-line information]. Available online at http://www.endocrine.niddk.nih.gov/pubs/acro/acro.htm through http://www.endocrine.niddk.nih.gov. Accessed October 2010.

Savage, M. et. al. (2010 June 23). The Continuum of Growth Hormone–IGF-I Axis Defects Causing Short Stature: Diagnostic and Therapeutic Challenges. Medscape Today from Clin Endocrinol. 2010;72(6):721-728. [On-line information]. Available online at http://www.medscape.com/viewarticle/722763 through http://www.medscape.com. Accessed October 2010.

Pagana, K. D. & Pagana, T. J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 879-880.

Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 626-631.

Kronenberg, H. et. al. (© 2008). Williams Textbook of Endocrinology, 11th Edition: Saunders Elsevier, Philadelphia, PA. Pp 891-906.

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