Sex hormone-binding globulin (SHBG)

SHBG (Sex hormone-binding globulin) is a protein produced in the liver that binds sex hormones such as testosterone and estrogen in the blood. This regulates how much of these hormones are free and thus biologically active.

High SHBG levels mean that less free testosterone or estrogen is available, which can occur in liver diseases or overactive thyroid conditions. Low levels lead to more free hormone and occur, for example, in cases of obesity, diabetes, or underactive thyroid conditions.