Free Vs. Bound Testosterone

Testosterone is the hormone responsible for puberty in boys and the development of secondary sex characteristics. These characteristics include facial hair, muscle mass and sex drive. One type of testosterone is "bound," and the other is "free."

Bound

• Bound testosterone is attached to another molecule such as globulin or protein. When the testosterone is attached to another molecule it is "deformed" and cannot fit into a receptor site. Since it cannot become active, it is excreted by the body.

Free

• Free testosterone is the amount of testosterone that floats through the blood on its own and is readily available for use by the body. This form of testosterone is the most active. In men 700 to 900 ng/dl (nanograms per deciliter) is the normal level of free testosterone.

Production

• Both men and women produce testosterone.

  In men, 95% of testosterone is created in the testes and the rest is produced in the adrenal glands. In women, testosterone is produced in the ovaries and the adrenal glands. Men produce almost ten times as much free and bound testosterone as women.

Misconceptions

• When getting testosterone levels tested, the results may be misleading. If the level of bound testosterone is within normal range, it is not necessarily an indication of healthy levels. The level of free testosterone is more important, because free testosterone is the one that the body uses more readily.

Complications

• Health problems that can decrease the level of testosterone in the body include testicular damage or infections or tumors of the pituitary gland, which controls production of the hormone.