A total serum testosterone test measures the total amount of testosterone in the blood. Testosterone is the primary androgenic (male) hormone. It is mainly produced in the testes in men and the ovaries and adrenal glands in women. It circulates in the blood bound to proteins (such as sex hormone-binding globulin (SHBG) and albumin) or free. It plays vital roles in sexual development, fertility, muscle and bone mass, fat distribution, and red blood cell production.