This test measures the level of sex hormone binding globulin (SHBG) in your blood. SHBG is a protein made by your liver. It binds tightly to three sex hormones found in both men and women: estrogen; dihydrotestosterone, or DHT; and testosterone. SHBG carries these three hormones throughout your blood. SHBG and testosterone levels may be ordered on an adult male to help determine the cause of infertility, a decreased sex drive, and erectile dysfunction, especially when total testosterone results are inconsistent with clinical signs. In women, small amounts of testosterone are produced by the ovaries and adrenal glands. Even slight increases in testosterone production can disrupt the balance of hormones and cause symptoms such as lack of menstruation (amenorrhea), infertility, acne, and male pattern hair growth (hirsutism). These symptoms and others are often seen with polycystic ovarian syndrome, a condition characterized by an excess production of androgens. SHBG and testosterone testing may be useful in helping to detect and evaluate excess testosterone production and/or decreased SHBG concentrations.