Sex hormone-binding globulin (SHBG) is a protein that binds tightly to the primary sex hormones testosterone, dihydrotestosterone, and estradiol (an estrogen). In this bound state, SHBG transports these hormones in the blood as biologically inactive forms. Therefore, changes in SHBG levels can affect the amount of hormone that is available to be used by the body’s tissues. The sex hormone-binding globulin test may be used to help evaluate men for low testosterone and women for excess testosterone production. A healthcare professional may order this test in conjunction with other tests to evaluate the status of a person’s sex hormones.
In men, SHBG and total testosterone levels may be ordered to help determine the cause of infertility, a decreased sex drive, or erectile dysfunction. In women, SHBG and testosterone testing may be useful in helping to detect and evaluate excess testosterone production and/or decreased SHBG concentrations and in evaluating women suspected of having polycystic ovary syndrome (PCOS). Although small amounts of testosterone are produced by the ovaries and adrenal glands, even slight increases can disrupt the balance of hormones. Currently, the SHBG test is not performed frequently or routinely. Primarily, this test is ordered when the total testosterone results do not seem to be consistent with clinical signs and symptoms, such as: sexual problems in men, and irregular menstruation and/or excess hair growth in women.