DATE: August 24, 2017
TIME: 10:00am PT, 1:00pm ET
Testosterone is a steroid hormone that stimulates development of male secondary sexual characteristics, but it is also synthesized in female at a much lower level. Testosterone circulates in blood system in different forms: bound to sex-hormone binding globulin (SHBG)/albumin and free. Free testosterone and albumin-bound testosterone are collectively known as bioavailable testosterone. Clinically, testosterone test is used for evaluation of men with possible hypogonadism, women with hirsutism, virilization, oligomenorrhea, and possible testosterone deficiency in women. In children, testosterone test is used to evaluate boys with delayed or precocious puberty and infants with ambiguous genitalia or virilization. In addition, it is useful for monitoring testosterone replacement and antiandrogen therapy as well as diagnosis of androgen-secreting tumor. Currently, the commonly used method is automated direct immunochemiluminescent assays because of ease of use, wide availability, and high throughput. The limitations of immunochemiluminescent assays are insufficient sensitivity and specificity as well as substantial inter-method variability. Lately there has been a trend towards switching to liquid chromatography-tandem mass spectrometry (LC-MS/MS) due to its high sensitivity and specificity. Limitation of total testosterone test is that it may not closely reflect the level of androgenism in individuals who have altered amount of SHBG. For those individuals, free or bioavailable testing are recommended. The methods for free testosterone testing include equilibrium dialysis, ultracentrifugation, analog analysis, and calculation based on SHBG. Bioavailable testosterone can be measured after ammonium sulfate precipitation to remove SHBG-bound testosterone or calculated based on serum total testosterone, SHBG, and albumin concentrations. Since multiple methods are available for serum testosterone testing and substantial inter-method variability, U.S. Centers for Disease Control and Prevention has established a Laboratory/Manufacturer Hormone Standardization Program to standardize serum total testosterone measurements. Many professional organizations including American Association of Clinical Endocrinologists, Endocrine Society, and Canadian Men’s Health Foundation have published practice guidelines and position statements on appropriate use of testosterone test. It is generally recommended that a reliable total testosterone assay can be used for initial testing for men. If initial values are low, free or bioavailable testosterone should be used for confirmation. Direct immunoassays cannot accurately measure the low serum testosterone levels found in women, children, and hypogonadal men. The Endocrine Society recommends testosterone methods that use extraction and purification prior to measurement. LC-MS/MS methods meet these recommendations. Because of increased sensitivity and specificity, LC-MS/MS has emerged as the method of choice in women, children, and hypogonadal men for testosterone testing.
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