Because SHBG is often low in women with hirsutism, free testosterone is elevated while the total testosterone concentration is normal. For patients with suspected plasma protein abnormalities, such as nephrotic syndrome, cirrhosis of the liver, or pregnancy, a bioavailable testosterone should be measured rather than a free testosterone. Testosterone levels are helpful in the assessment of androgen status in male hypogonadism, hirsutism, virilization, acne, and amenorrhea. Women with Cushing's syndrome, hirsutism, or adrenal or ovarian androgen secreting tumors. Men with Cushing's disease or those receiving glucocorticoid therapy.
Bioavailable testosterone is an assessment of the biologically active testosterone in serum.
Measurement of testosterone binding sites. Steroid assay by binding protein . Karolinska Institute, 225-238. Rosner W. Errors in the measurement of plasma free testosterone. Calculation of free and bound fractions of testosterone and estradiol-17b to human plasma proteins at body temperature.