SHBG is the protein that carries around estrogen, testosterone, and DHT, another form of testosterone. Think of SHBG like a car that allows the hormones to go on the highway system of our bodies, our blood vessels. When hormones like testosterone are bound to this protein, they don’t have any action on the body. Only hormones that are out of a car, a pedestrian if you will, are able to affect the body in some way. We call these hormones Free Hormones, such as free testosterone.