To evaluate androgen excess or deficiency related to gonadal function, adrenal function, or tumor activity.
In males, testosterone levels are helpful for the diagnosis of hypogonadism, hypopituitarism and impotence (low values). Monitoring testosterone replacement therapy.
In females, levels may be requested to investigate the cause of hirsutism, anovulation, amenorrhea, virilization, masculinizing tumors of the ovary, tumors of the adrenal cortices, and congenital adrenal hyperplasia (high values).
In children, may be helpful to investigate issues related to puberty and development, as well as evaluation of infants with ambiguous genitalia or virilization.
Separate serum from the blood within 60 minutes of venipuncture. Specimen must be free of particulate matter including fibrin. Specimens can be thawed and frozen up to two times.
Testosterone secretion is episodic. Serum testosterone levels in adult males peak in the early morning (7am), decreasing about 25% to the evening (minimum at about 8pm). Levels increase after exercise and decrease after immobilization and after glucose load.
Most circulating testosterone is bound to sex hormone-binding globulin (SHBG), which in males also is called testosterone-binding globulin. A lesser fraction is albumin bound and a small proportion exists as free hormone. It was initially understood that only the free testosterone was thought to be the biologically active component. However, testosterone weakly bound to serum albumin which dissociates freely in the capillary bed, becomes readily available for tissue uptake. Therefore, all non-SHBG-bound testosterone is considered bioavailable.
Male testosterone levels decrease with age; it is generally a gradual decrease in testosterone levels and not a sudden loss of reproductive capability. Changes seen with lower testosterone with aging include decrease in bone mass, cognitive function, erectile function, libido, muscle strength and sense of wellbeing.
Low testosterone concentrations can be caused by testicular failure (primary hypogonadism) or inadequate stimulation by pituitary gonadotropins (secondary hypogonadism). Hypogonadism often has high SHBG levels, therefore, the measurement of free or bioavailable testosterone has been recommended when total testosterone levels are normal in men with symptoms of androgen deficiency.
In females, ovary and adrenal glands produce some testosterone, but the majority of the testosterone in women is derived from the peripheral conversion of other steroids. Often, the first sign of testosterone excess in women is the development of male pattern hair growth, which is referred to as hirsutism. It has been observed that some women experience hair growth similar to that caused by increased testosterone due to racial or genetic causes and not due to excessive androgens. Measurement of the testosterone may help to distinguish racial or genetic causes of hirsutism from the abnormal pathology, particularly in women with mixed ethnic backgrounds.
Reference intervals for Pediatric population has not been established and are adopted from literature.Serum and plasma values should not be used interchangeably. Values obtained from different Immunoassays may differ and cannot be used interchangeably. Results obtained by LC/Tandem mass spectrometry are lower than results by Immunoassays.
Testosterone levels can fluctuate substantially between different days, and sometimes even more frequently. Assessment of androgen status should be based on more than a single measurement.
Testosterone results should be interpreted in light of the total clinical presentation of the patient, including: symptoms, clinical history, data from additional tests and other appropriate information.
Measurement of total testosterone is often sufficient for diagnosis, particularly if it is combined with measurements of LH (Luteinizing Hormone) and FSH (Follicle Stimulating Hormone). However, these tests may be insufficient for diagnosis of mild abnormalities of testosterone homeostasis, particularly if the abnormalities in SHGB (Sex Hormone Binding Globulin) function or levels are present. Additional measurements of bioavailable testosterone or/and free testosterone are recommended in this situation.
Recommendations: The Endocrine Society and American Society of Andrology recommends using total testosterone measurement preferably obtained on more than one morning sample as a screening test for hypogonadism in men. Most direct Immunoassays distinguish between concentrations found in classic hypogonadism and normal levels and allows fast turnaround time. Direct Immunoassays have been found to be adequate for identifying but not accurately quantifying elevated testosterones in women. Testosterone determinations in children should be assessed using assays with sufficient sensitivity and in conjunction with appropriate reference intervals (J Clin Endocrinol Metab. 2007; 92:405).
For the diagnosis of androgen dysfunction in females and children, as well as monitoring hypogonadal men, it is recommended that high sensitivity and specificity assays able to measure very low levels of testosterone concentrations should be used. Direct Immunoassays are not able to accurately measure at very low levels.
Current method does not show any interference with 5-alpha-DHT, testosterone sulfate, 19-hydroxytestosterone, DHEA and Androstenediol.