SHBG is a protein produced primarily in the liver, although the testes, uterus, brain, and placenta also synthesize it. It serves as a transport carrier, shuttling estrogen and testosterone to sex hormone receptors throughout your body. SHBG also safeguards these vital hormones from degrading too rapidly and prevents their clearance from the body.

It acts as the master regulator of your sex hormone levels, maintaining the balance between estrogen and testosterone critical to overall health in aging humans.

Optimal SHBG 30nmol/L
Usually goes up as men age and binds tightly to total testosterone therefore less free or bioavailable T.
This is the hallmark of aging patients. This is why many physicians who only test for total testosterone allow many men who are andropausal with healthy/optimal levels of total and low levels of free, slip through the cracks. A man can have a Total Testosterone of 800 ng/dl and a high SHBG and still be andropausal due to elevated SHBG lowering FreeT

Free testosterone is the important level to evaluate.

SHBG can go down with T therapy.
Serum Albumin - also loosely binds T in serum. However this is loosely bound and still can be used as bioavaliable. This leaves only 1-2% free testosterone.


New evidence further indicates that the SHBG molecule itself plays another key role in the body: conveying essential signals to the heart, the brain, and adipose (fat) tissue that ensure their optimal function.There’s even a special SHBG receptor molecule on cell surfaces that functions much like the ubiquitous vitamin D receptor protein, helping cells communicate with one another.In other words, SHBG itself functions much like a hormone.

Knowing your SHBG levels, along with testosterone and estrogen, gives you and your doctor a more precise picture of your overall health—and enables you to take preventive measures against life-threatening conditions for which you may be at greater risk.