Testosterone, Free, Serum


Measurements of free testosterone may be more appropriate than measurements of total testosterone. It is independent of changes in concentrations of the principal testosterone transport protein, sex hormone-binding globulin. In adult males, testosterone levels show a diurnal variation with the highest levels detected in the early morning and the lowest in the evening. See Also Testosterone, Total, Serum


Free testosterone levels are valuable for investigating patients with hirsutism, loss of libido and male hypogonadism. High levels of free testosterone may indicate an adrenocortical tumor, androgen-secreting ovarian tumor or pituitary overproduction of ACTH. Conditions such as hypogonadism, hypopituitarism, estrogen therapy, and some cases of Kleinfelter’s syndrome are associated with decreased levels of testosterone.

Sample Type, Quantity & Conditions

1 ml Serum Stability: 12 Hours at 2-8 °C 30 Days at -20 °C

Special Precautions

Normal Range

Male: 15-50 pg/mL Female: Up to 6.5 pg/mL

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