Testosterone (free) + SHBG
Testosterone free (ISSAM) blood test is calculated from the 3 tests performed here:
These three values are also reported separately.
Testosterone is the main male sex hormone. Testosterone is needed for normal development of the male sex characteristics. In addition, testosterone is needed for proper sperm production.
Most of the testosterone is bound to the transport protein SHBG (Sex Hormone Binding Globulin) and is therefore not biologically active. This test measures the amount of unbound, biologically active testosterone.
The test also measures the amount of Sex Hormone Binding Globulin (SHBG) in blood. SHBG is a protein (globulin) produced by the liver that is able to strongly bind testosterone and estradiol. SHBG then transports these hormones in an inactive form through the blood throughout the body. Testosterone inhibits the production of SHBG while estradiol stimulates it.
Men mainly produce testosterone in the testes and very little estradiol. Women produce mostly estradiol in the ovaries (ovaries) and a little testosterone in ovaries and in the adrenal gland. Change in the amount of SHBG affects the amount of testosterone that is freely available.
Click here for the Free Testosterone Calculator