At a Glance
Why Get Tested?
To evaluate whether the concentration of sex hormone binding globulin (SHBG) is affecting the amount of testosterone available to the body's tissues
When to Get Tested?
When your total testosterone results seem inconsistent with clinical signs, suggesting a testosterone deficiency or excess production
A blood sample drawn from a vein in your arm
Test Preparation Needed?
The Test Sample
What is being tested?
The sex hormone binding globulin (SHBG) test measures the concentration of SHBG in the blood. SHBG is a protein that is produced by the liver and binds tightly to testosterone, dihydrotestosterone (DHT), and estradiol (an estrogen). In this bound state, it transports them in the blood as a biologically inactive form. The amount of SHBG in circulation is affected by age and sex, by decreased or increased testosterone or estrogen production, and can be affected by certain diseases and conditions such as liver disease, hyperthyroidism or hypothyroidism, and obesity.
Changes in SHBG levels can affect the amount of testosterone that is available to be used by the body's tissues. Normally, about 40% to 60% of testosterone is bound to SHBG, with most of the rest weakly and reversibly bound to albumin, the main protein in the blood. Only about 2% is immediately available to the tissues as free testosterone.
A total testosterone test does not distinguish between bound and unbound testosterone but determines the overall quantity of testosterone. In many cases, this is sufficient to evaluate excessive or deficient testosterone production. However, if a person's SHBG level is not normal, then the total testosterone may not be an accurate representation of the amount of testosterone that is available to the person's tissues.
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?
No test preparation is needed.
Ask a Laboratory Scientist
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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 for Current Review
Anawalt, B. (Revised 2010 January). Male Reproductive Endocrinology. The Merck Manual for Healthcare Professionals [On-line information]. Available online through http://www.merckmanuals.com. Accessed January 2012.
Dandona, P and Rosenberg, M. (2010 May 10). A Practical Guide to Male Hypogonadism in The Primary Care Setting: Clinical Presentation and Diagnosis. Medscape Today News from Int J Clin Pract. 2010;64(6):682-696 [On-line information]. Available online at http://www.medscape.com/viewarticle/721069_4 through http://www.medscape.com. Accessed January 2012.
Peter, A. et. al. (2010 December 16). Relationships of Circulating Sex Hormone–Binding Globulin with Metabolic Traits in Humans. Medscape Today News from Diabetes. 2010;59 (12) [On-line information]. Available online at http://www.medscape.com/viewarticle/733605 through http://www.medscape.com. Accessed January 2012.
(Updated © 1995-2012). Test ID: SHBG9285 Sex Hormone-Binding Globulin (SHBG), Serum Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/9285 through http://www.mayomedicallaboratories.com. Accessed January 2012.
(Updated 2011 July). Hypogonadism, Male. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/HypogonadismMale.html?client_ID=LTD#tabs=0 through http://www.arupconsult.com. Accessed January 2012.
Lucidi, R. et. al. (Updated 2011 October 25). Polycystic Ovarian Syndrome. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/256806-overview through http://emedicine.medscape.com. Accessed January 2012.
Pagana, K. D. & Pagana, T. J. (© 2011). Mosby’s Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 928-930.
Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Burtis CA, Ashwood ER, Bruns DE, eds. St. Louis: Elsevier Saunders; 2006, 2011-2012.
Maggio M, et al. Sex hormone binding globulin levels across the adult lifespan in women - The role of body mass index and fasting insulin. J Endocrinol Invest. 2008 July; 31(7): 597–601. Available online at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2648802/ through http://www.ncbi.nlm.nih.gov. Accessed February 2012.
Kelly JA, Vankrieeken L. Sex hormone binding globulin and the assessment of androgen status. Available online through http://www.medical.siemens.com. Accessed February 2012.
Sources Used for 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.
(© 2004). Sex Hormone Binding Globulin. ARUP's Guide to Clinical Laboratory Testing [On-line information]. Available online at http://www.arup-lab.com/guides/clt/tests/clt_193b.jsp#1147406 through http://www.arup-lab.com.
(© 2004). Testosterone, Bioavailable and Sex Hormone Binding Globulin. ARUP's Guide to Clinical Laboratory Testing [On-line information]. Available online at http://www.arup-lab.com/guides/clt/tests/clt_225b.jsp#1148913 through http://www.arup-lab.com.
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Anawalt, B. (2007 June Reviewed). Male Reproductive Endocrinology, Introduction. Merck Manual for Healthcare Professionals [On-line information]. Available online at http://www.merck.com/mmpe/sec17/ch227/ch227a.html?qt=SHBG&alt=sh through http://www.merck.com. Accessed on 7-30-08.