Testosterone, Total

Overview:

Testosterone testing is used to evaluate androgen excess or deficiency related to gonadal function, adrenal function, or tumor activity. Testosterone levels may be helpful in men for the diagnosis of hypogonadism, hypopituitarism, Klinefelter syndrome, and impotence (low values). Testosterone levels may be requested in women 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). Testosterone levels in children may be helpful to investigate issues related to puberty and development as well as the aforementioned. For testosterone measurements in females and children, use of Testosterone, Total, Women, Children, and Hypogonadal Males, LC/MS-MS [070001], which employs liquid chromatography/tandem mass spectrometry (LC/MS-MS), is recommended.

As with all tests containing monoclonal mouse antibodies, erroneous findings may be obtained from samples taken from patients who have been treated with monoclonal mouse antibodies or have received them for diagnostic purposes.1 In rare cases, interference due to extremely high titers of antibodies to streptavidin and ruthenium can occur.1 The test contains additives, which minimize these effects.

This immunoassay is intended for the in vitro quantitative determination of testosterone in human serum and plasma.

Testosterone is the principal androgen in men.2,3 The production of testosterone by the male testes is stimulated by luteinizing hormone (LH), which is produced by the pituitary. LH secretion is, in turn, inhibited through a negative feedback loop by increased concentrations of testosterone and its metabolites. Most of the testosterone in males is produced by the Leydig cells of the testes and is secreted into the seminiferous tubule, where it is complexed to a protein made by the Sertoli cells. This results in the high local levels of testosterone that are required for normal sperm production.

Diminished testosterone production is one of many potential causes of infertility in males.3,4 Low testosterone concentrations can be caused by testicular failure (primary hypogonadism) or inadequate stimulation by pituitary gonadotropins (secondary hypogonadism). Since men with hypogonadism often have high SHBG levels, the measurement of free or bioavailable testosterone has been advocated when total testosterone levels are normal in men with symptoms of androgen deficiency.5 Significant physiological changes occur in men as they age, in part due to a gradual decline in testosterone levels.6,7 It is generally accepted that the principal cause of this age-related decrease in testosterone production is testicular failure, although diminished gonadotropin production may play a role.5 By 75 years of age, the average male testosterone drops to 65% of average level in young adults. “Andropause” is a term that has been used to refer to the constellation of symptoms associated with the age-related decline in testosterone production in men.5,8 The adult male reference range for testosterone was established by Travison and coworkers through an epidemiologic study that included men from different geographic regions of the United States and Europe.9 Testosterone measurment was harmonized to the Center for Disease Control reference method.9 The reference population included only men younger than 40 years of age who had a BMI less than 30. Much smaller amounts of testosterone and dihydrotestosterone are produced in women than in men.2,3 Weaker adrenal androgens and ovarian precursor molecules including androstenedione, DHEA, and DHEA sulfate can have significant androgenic effects in women. The 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.1,3,4,10 It should be noted 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. Women with more excessive testosterone levels may also experience virilization, with symptoms including increased muscle mass, redistribution of body fat, enlargement of the clitoris, deepening of the voice, and acne and increased perspiration. These women can also suffer from androgenic alopecia, the female equivalent of male pattern baldness.

Many women with slowly progressive androgenic symptoms are diagnosed as having polycystic ovary syndrome (PCOS).10-12 PCOS is relatively common, affecting approximately 6% of women of reproductive age.6 Women with this complex syndrome experience symptoms of androgen excess associated with menstrual abnormalities and infertility. Most women with the syndrome have polycystic ovaries that can be detected by ultrasonography, although this finding is not essential for diagnosis.3,4,13 Chronic anovulation experienced by patients with PCOS increases their risk of developing endometrial cancer. Women with PCOS are often overweight and are likely to suffer from insulin resistance putting them at increased risk for developing type 2 diabetes mellitus.2,11 Obesity and insulin resistance can result in acanthosis nigricans, a skin condition that is characterized by hyperpigmented, velvety plaques of body folds.2 Lipid abnormalities, including decreased high-density lipoprotein cholesterol levels and elevated triglyceride levels as well as impaired fibrinolysis, are seen in women with PCOS.11 Cardiovascular disease is more prevalent, and women with PCOS have a significantly increased risk for myocardial infarction.11

1. Testosterone on Elecsys 1010/2010 and Modular Analytics E170, package insert 2007-04, V 10, Indianapolis, IN: Roche Diagnostics, 2007.

2. Ismail AA, Astley P, Burr WA, et al. The role of testosterone measurement in the investigation of androgen disorders. Ann Clin Biochem. 1986; 23(Pt 2):113-134. PubMed 3532913

3. Gronowski AM, Landau-Levine M. Reproductive endocrine function. In: Burtis CA, Ashwood ER, edsTietz Textbook of Clinical Chemistry. 3rd ed. Philadelphia, Pa: WB Saunders Co;1999:1601-1641.

4. Petak SM, Baskin HJ, Bergman DA, et al. AACE Clinical Practice Guidelines for the evaluation and treatment of hypogonadism in adult male patients. Endocrinol Pract. 1996; 2:440-453.

5. Bain J. Andropause. Testosterone replacement therapy for aging men. Can Fam Physician. 2001; 47:91-97. PubMed 11212438

6. Leifke E, Gorenoi V, Wichers C, et al. Age-related changes of serum sex hormones, insulin-like growth factor-1 and sex-hormone binding globulin levels in men: Cross-sectional data from a healthy male cohort. Clin Endocrinol. 2000; 53(6):689-695. PubMed 11155090

7. Basaria S, Dobs AS. Hypogonadism and androgen replacement therapy in elderly men. Am J Med. 2001; 110(7):563-572. PubMed 11343670

8. Bhasin S, Bagatell CJ, Bremner WJ, et al. Issues in testosterone replacement in older men. J Clin Endocrinol Metab. 1998; 83(10):3435-3448. PubMed 9768643

9. Travison TG, Vesper HW, Orwoll E, et al. Harmonized reference ranges for circulating testosterone levels in men of four cohort studie