Sex hormone binding globulin (SHBG) is a protein produced by the liver, that binds tightly to the hormones testosterone, dihydrotestosterone (DHT), and oestradiol (an estrogen).
SHBG transports these hormones in the blood as biologically inactive forms. This test measures the level of SHBG in the blood and is most often used to help evaluate testosterone deficiency or excess.
Read more about SHBG blood test.
In men, about 45% to 65% of testosterone in blood is normally bound to SHBG, with the remainder weakly and reversibly bound to albumin (the main protein in the blood). Only about 2% to 3% of testosterone is immediately available to the tissues as free testosterone. Testosterone that is weakly bound to albumin is also bioavailable and can be readily taken up by the body's tissues.
In women, slightly more testosterone (66% to 78%) is bound to SHBG. In women, SHBG plays an integral role in regulating the levels of bioavailable male sex hormones (androgens) and estrogens circulating throughout the body. As SHBG has a higher affinity for the androgens testosterone and DHT, women with low SHBG may have signs and symptoms related to androgen excess.
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 excess or deficient testosterone production. However, if a person's SHBG level is not normal, then the total testosterone may be an inaccurate representation of the amount of testosterone that is available to the person's tissues.
An SHBG test may be performed when a person's signs and symptoms do not correlate with the results of a total testosterone test.
What happens next?
The lab sends the results to your personal dashboard, with comments from both a doctor and a nutritionist. If results are abnormal, we recommend seeing a doctor and, if appropriate, booking an appointment with a Nordic Wellth nutrition lifestyle specialist.