Free Testosterone vs. Bound Testosterone

The need for male testosterone therapy is determined largely by your lab tests. Aaccurate hormone testing is essential, since the results will determine the right course of treatment. Yet, most tests only look at your total testosterone, not your free testosterone levels. What’s the difference, and why is this important?

Total Testosterone

There isn’t just one type of testosterone in the body; instead, there are actually three. Two of these are bound testosterone, while one is free. When you visit the lab to have your testosterone levels tested, most labs will test for total testosterone, which measures all three types together for one grand total. The problem with this is that the body can’t really access bound testosterone, so that number really shouldn’t count.

When testosterone is “bound,” that means that the testosterone molecule is tightly connected to another type of molecule. Testosterone can be bound either to a special protein molecule called SHBG (sex hormone binding globulin) or to albumin, which is a blood component. The majority of testosterone in the blood, about 60-70 percent, is bound to SHBG. Between 30-40 percent is linked to albumin, leaving about 2 percent of truly free testosterone circulating through the body.

When testosterone is bound to SHBG, it’s not available for the body to use. However, the link between albumin and testosterone is weak enough that albumin-bound testosterone can still enter cells; because of this, albumin-bound testosterone is sometimes counted as part of free testosterone.

When the amount of testosterone that’s biologically available for the body to use falls too low, then men develop symptoms of Low T. At our clinic in San Diego, bioidentical hormone replacement therapy is the ideal solution to restore those levels back up to normal again.

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