Free Testosterone
Testosterone is an androgen synthesized by the Leydig cells of the testes in males and by the adrenal cortex and the stroma of the ovary in females. Testosterone measurement is used in the investigation of hyperandrogenicity in women and hypogonadal states in men. Free testosterone (fraction of testostosterone that is not bound to protein) levels are less susceptible to changes in concentration of the principal testosterone transport protein SHBG (sex hormone binding globulin). Thus, abnormal free testosterone concentration is more reliable indicator of sex hormone imbalance than that of total testosterone.