Test Details: Sex hormone binding globulin (SHBG) is a protein produced by the liver that transports the hormones testosterone (an androgen), dihydrotestosterone (DHT) (an androgen), and estradiol (an estrogen) in the blood as biologically inactive forms. Changes in SHBG levels can affect the amount of hormone that is available to be used by the body’s tissues. This test measures the level of SHBG in the blood and is most often used to help evaluate patients for testosterone deficiency or excess.