The Sex Hormone-Binding Globulin (SHBG) test measures the level of SHBG, a protein produced by the liver that binds to sex hormones such as testosterone and estrogen in the blood. SHBG regulates the availability of these hormones to tissues and plays a key role in hormonal balance. This test is used to assess hormonal imbalances, diagnose conditions related to sex hormone levels, and evaluate issues like reproductive disorders or metabolic syndrome.