Understanding Total and Free Testosterone Levels

Total testosterone, true to its name, measures the total amount of testosterone in the body. Total testosterone includes testosterone that is bound to carrier proteins as well as free testosterone. Testosterone that is bound to proteins is not usable by the body whereas free testosterone is readily available for use. Most of the testosterone in the body is bound to protein in an unusable form but it serves as a reservoir in which more can be released when needed. When measuring labs it is important to evaluate both total and free testosterone as it provides a more accurate assessment of what is going on in the body. Looking at total testosterone alone does not provide enough insight because it does not offer any information about the testosterone that is bioavailable for use. This becomes increasingly problematic for men as they age because not only does testosterone decline but sex hormone binding globulin (SHBG), the most prevalent binding protein, increases. This means that more testosterone ends up bound in an unusable form. Total testosterone can often appear normal but free testosterone, the kind available for use declines. You see this in tandem with the emergence of symptoms of low testosterone. Too often men are made to feel like the symptoms are all in their head when there is a very real reason they are experiencing them. Evaluating free testosterone is an important aspect of evaluating testosterone deficiency and managing testosterone replacement therapy appropriately and should not be overlooked, although all too often it is.