IGF-1

Share this page:
Also known as: Somatomedin C
Formal name: Insulin-like Growth Factor - 1
Related tests: Growth Hormone (GH), Glucose, Glucose Tolerance Test, IGFBP-3 (IGF-Binding Protein 3)

At a Glance

Why Get Tested?

To identify diseases and conditions caused by deficiencies and overproduction of growth hormone (GH), to evaluate pituitary function, and to monitor the effectiveness of GH treatment

When to Get Tested?

When you have symptoms of slow growth, short stature, and delayed development (in children) or decreased bone density, reduced muscle strength, and increased lipids (in adults) that suggest insufficient GH and IGF-1 production; when you have symptoms of gigantism (in children) or acromegaly (in adults) that suggest excess GH and IGF-1 production; during and after treatment for GH abnormalities; as part of an evaluation of pituitary function

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

Generally none, unless instructed to fast

The Test Sample

What is being tested?

The insulin-like growth factor-1 (IGF-1) test is an indirect measure of the average amount of growth hormone (GH) being produced by the body. IGF-1 and GH are polypeptide hormones, small proteins that are vital for normal bone and tissue growth and development. GH is produced by the pituitary gland, a grape-sized gland located at the base of the brain behind the bridge of your nose. GH is secreted into the bloodstream in pulses throughout the day and night with peaks that occur mostly during the night. 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. IGF-1 mirrors GH excesses and deficiencies, but its level is stable throughout the day, making it a useful indicator of average GH levels.

Like GH, IGF-1 levels 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 conditions such as 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.

Deficiencies early in life 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 densities, less muscle mass, and altered lipids. However, testing for GH deficiency or IGF-1 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 only 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 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 life span. 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.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

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.

The Test

Common Questions

Ask a Laboratory Scientist

Form temporarily unavailable

Due to a dramatic increase in the number of questions submitted to the volunteer laboratory scientists who respond to our users, we have had to limit the number of questions that can be submitted each day. Unfortunately, we have reached that limit today and are unable to accept your inquiry now. We understand that your questions are vital to your health and peace of mind, and recommend instead that you speak with your doctor or another healthcare professional. We apologize for this inconvenience.

This was not an easy step for us to take, as the volunteers on the response team are dedicated to the work they do and are often inspired by the help they can provide. We are actively seeking to expand our capability so that we can again accept and answer all user questions. We will accept and respond to the same limited number of questions tomorrow, but expect to resume the service, 24/7, as soon as possible.

Article Sources

« Return to Related Pages

NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Sources Used in Current Review

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.

Sources Used in Previous Reviews

Thomas, Clayton L., Editor (1997). Tabers 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.