his test measures the amount of unattached, or "free," testosterone in your blood.
Testosterone is a male sex hormone (androgen) that helps male features develop. Testosterone is made in the testes and the adrenal glands. It causes the changes that occur in boys during puberty. Testosterone helps hair and muscles grow. It also helps the penis and testes grow. Testosterone also causes a boy's voice to deepen. Men continue to make testosterone. It boosts sex drive and helps make sperm.
Women's ovaries also make small amounts of testosterone. It helps many organs and body processes in women.
The pituitary gland in your brain controls the amount of testosterone your body makes.
Most of the testosterone in your blood attaches to 2 proteins: albumin and sex hormone binding globulin (SHBG). Some testosterone is not attached to proteins, or free. Free testosterone and albumin-bound testosterone are also referred to as bioavailable testosterone. This is the testosterone that is easily used by your body.
If your healthcare provider thinks that you have low or high testosterone, he or she will first test total testosterone levels. This looks at all 3 types of testosterone. The free testosterone can help give more information when total testosterone is low.
Both men and women can have health problems because of low or high levels of testosterone. Women with high levels of testosterone may have polycystic ovary syndrome (PCOS). This condition can cause: