Sex hormone binding globulin (SHBG) is a plasma protein which transports the sex steroids testosterone, DHT and estradiol in the blood. SHBG is produced by the liver. The amount of SHBG in circulation is affected by age and sex, by decreased or increased testosterone or estrogen production, and can be affected by certain diseases and conditions such as liver disease, hyperthyroidism or hypothyroidism, and obesity. Changes in SHBG levels can affect the amount of testosterone that is available to be used by the body’s tissues. This test is primarily ordered to evaluate the status of a patient’s androgens - the male hormones. Although SHBG is not usually ordered to diagnose or monitor these conditions, INCREASES in SHBG are seen with liver disease, hyperthyroidism, anorexia, and estrogen use (hormone replacement therapy and oral contraceptives). DECREASES in SHBG are seen with obesity, hypothyroidism, androgen use, and Cushing’s disease.