SHBG

Also known as: Testosterone-estrogen Binding Globulin (TeBG)

Formal name: Sex Hormone Binding Globulin

Related tests: Testosterone, Free Testosterone, Bioavailable Testosterone

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. It binds tightly to testosterone, dihydrotestosterone (DHT), and estradiol (an estrogen) and transports them in the blood in a metabolically 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, and most of the rest is weakly and reversibly bound to albumin. Only about 2% is immediately available to the tissues as free testosterone.

A total testosterone test does not distinguish between bound and unbound testosterone; it determines the overall quantity of testosterone. In many cases, this is sufficient to evaluate excessive or deficient testosterone production; but, if a patient’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 a patient’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.