Sex Hormone-Binding Globulin (SHBG)
Your total testosterone can look great while a liver protein quietly locks most of it away.
Grounded in the research on sex hormone-binding globulin
the courier
SHBG is a glycoprotein your liver pumps into your bloodstream to ferry sex hormones around. It grabs testosterone, DHT, and estradiol and holds them. The catch: a hormone clamped to SHBG is parked. It can't enter a cell or fire a receptor. So SHBG isn't a side number on a lab panel. It's the gatekeeper deciding how much of your testosterone actually gets to do anything.
the math nobody mentions
Run the numbers and it's stark. Only about 1 to 2 percent of your testosterone floats free. Roughly 65 percent is bound tight to SHBG, locked out. The rest rides on albumin, gripped loosely enough to break off when tissue needs it. That free slice plus the albumin slice is your bioavailable testosterone, the part that works. The SHBG-bound 65 percent is a holding tank, not a usable balance.