TEST UPDATE - TCL€¦ · The measurement of free testosterone, albumin bound testosterone, and Sex...
4
Carmen L. Wiley, PhD, DABCC, FACB TEST UPDATE Quick Facts For more information, please contact your local marketing representative Measurement of testosterone is valuable in the evaluation of androgen disorders. There are two laboratory methods available – immunoassay and LC-MS/MS. Total testosterone measurement includes free testosterone, albumin bound testosterone and Sex Hormone Binding Globulin (SHBG) bound testosterone. Suspected low levels of testosterone are best measured by LC-MS/MS. Age and gender is required information as reference ranges are age and gender specific. Testosterone Testing: What Test Should I Order? Total Testosterone The measurement of free testosterone, albumin bound testosterone, and Sex Hormone Binding Globulin (SHBG) bound testosterone. Free Testosterone The measurement of freely circulating testosterone. Free testosterone can also be calculated. After measuring the total testosterone and SHBG a mathematical formula is used to subtract the testosterone bound to albumin and SHBG, leaving you with the calculated free testosterone level. Bioavailable Testosterone Represents the fraction of circulating testosterone that readily enters cells. This is both the free testosterone and the albumin bound testosterone. The binding between testosterone and albumin is not very strong and is easily reversed; so the term bioavailable testosterone refers to the sum of free testosterone plus albumin-bound testosterone. After measuring the total testosterone, SHBG, and albumin a mathematical formula is used calculate the bioavailable testosterone. More simply stated, this is the testosterone that is not bound to SHBG. CLINICAL APPLICATION The measurement of circulating testosterone is clinically relevant in the investigation of androgen disorders in men, women and children. MEN In men, testosterone analysis is used to evaluate the endocrine activity of the testis and for diagnosis of testosterone deficiency. This test may be ordered when infertility is suspected or if the patient has a decreased sex drive or erectile dysfunction, all of which can result from low testosterone levels. Some other symptoms include lack of beard and body hair, decreased muscle mass, and gynecomastia. Measurement of testosterone in men is also recommended in the monitoring of patients with metastatic prostate cancer treated with gonadotropin-releasing hormone analogs and/or by antiandrogen therapy, and as a means of checking that the testosterone concentration has decreased to extremely low levels. WOMEN In women, testosterone is frequently measured as part of the investigation of irregular or no menstrual periods, alopecia, acne, and hirsutism. Testosterone levels can rise because of polycystic ovarian syndrome (PCOS) and testosterone measurement can aid in the diagnosis of PCOS. Testosterone measurements are also used for detection of androgen- secreting tumors of ovarian and adrenal origin, and to determine the minimum drug dose required to suppress androgen secretion in hyperandrogenic women. CHILDREN In children, testosterone concentration is determined for the diagnosis, treatment, and gender assignment of newborns or young infants with ambiguous genitalia. The testosterone concentration can also be used to determine pubertal stage (Tanner Stage) in association with physical examination in the follow-up of children with precocious or delayed puberty. Additionally, testosterone is also closely monitored in the follow-up of patients with congenital adrenal hyperplasia resulting from 21-hydroxylase deficiency. 050912 Testosterone_TCL_TEST_0003
Transcript of TEST UPDATE - TCL€¦ · The measurement of free testosterone, albumin bound testosterone, and Sex...
Carmen L. Wiley, PhD, DABCC, FACB
TEST UPDATE
Quick Facts
For more information, please contact your
local marketing representative
Measurement of testosterone is valuablein the evaluation of androgen disorders.
There are two laboratory methods available – immunoassay andLC-MS/MS.
Total testosterone measurement includes free testosterone, albumin bound testosterone and Sex Hormone Binding Globulin (SHBG) bound testosterone.
Suspected low levels of testosterone are best measured by LC-MS/MS.
Age and gender is required information as reference ranges are age and gender specific.
Testosterone Testing: What Test Should I Order?Total TestosteroneThe measurement of free testosterone, albumin bound testosterone, and Sex Hormone Binding Globulin (SHBG) bound testosterone.
Free TestosteroneThe measurement of freely circulating testosterone. Free testosterone can also be calculated. After measuring the total testosterone and SHBG a mathematical formula is used to subtract the testosterone bound to albumin and SHBG, leaving you with the calculated free testosterone level.
Bioavailable TestosteroneRepresents the fraction of circulating testosterone that readily enters cells. This is both the free testosterone and the albumin bound testosterone. The binding between testosterone and albumin is not very strong and is easily reversed; so the term bioavailable testosterone refers to the sum of free testosterone plus albumin-bound testosterone. After measuring the total testosterone, SHBG, and albumin a mathematical formula is used calculate the bioavailable testosterone. More simply stated, this is the testosterone that is not bound to SHBG.
CLINICAL APPLICATION
The measurement of circulating testosterone is clinically relevant in the investigation of androgen disorders in men, women and children.
MENIn men, testosterone analysis is used to evaluate the endocrine activity of the testis and for diagnosis of testosterone deficiency. This test may be ordered when infertility is suspected or if the patient has a decreased sex drive or erectile dysfunction, all of which can result from low testosterone levels. Some other symptoms include lack of beard and body hair, decreased muscle mass, and gynecomastia. Measurement of testosterone in men is also recommended in the monitoring of patients with metastatic prostate cancer treated with gonadotropin-releasing hormone analogs and/or by antiandrogen therapy, and as a means of checking that the testosterone concentration has decreased to extremely low levels.
WOMENIn women, testosterone is frequently measured as part of the investigation of irregular or no menstrual periods, alopecia, acne, and hirsutism. Testosterone levels can rise because of polycystic ovarian syndrome (PCOS) and testosterone measurement can aid in the diagnosis of PCOS. Testosterone measurements are also used for detection of androgen- secreting tumors of ovarian and adrenal origin, and to determine the minimum drug dose required to suppress androgen secretion in hyperandrogenic women.
CHILDRENIn children, testosterone concentration is determined for the diagnosis, treatment, and gender assignment of newborns or young infants with ambiguous genitalia. The testosterone concentration can also be used to determine pubertal stage (Tanner Stage) in association with physical examination in the follow-up of children with precocious or delayed puberty. Additionally, testosterone is also closely monitored in the follow-up of patients with congenital adrenal hyperplasia resulting from 21-hydroxylase deficiency.
050912Testosterone_TCL_TEST_0003
Testosterone Testing: What Test Should I Order?
CLINICAL BACKGROUND
About 60% of circulating testosterone is strongly bound to Sex Hormone-Binding Globulin (SHBG). And about 40% of the hormone is bound to albumin and only 1 to 4% exists as free hormone.
Historically, only the free testosterone was thought to be the biologically active component. However, testosterone that is weakly bound to serum albumin will dissociate freely in the capillary bed, thereby becoming readily available for tissue uptake. All non-SHBG bound testosterone is therefore considered bioavailable.
LABORATORY METHODS
We have two different methods for measuring testosterone:1. Immunoassays2. Liquid chromatography followed by tandem mass fffffspectrometry (also called LC-MS/MS).
Immunoassays are chemical tests used to quantify a specific substance, testosterone in this case, in a blood sample, using an immunological reaction.
Immunoassays measure the formation of antibody-antigen complexes and detect them via an indicator reaction. Although immunoassays are both highly sensitive and specific, false positive and negative results may occur.
Also, recent studies suggest that the majority of immunoassays utilized for testosterone measurement have acceptable performance for samples from healthy men, but results for specimens from females and children can be inaccurate because these immunoassays lose sensitivity and specificity at the very low levels found in these patients.
Mass spectrometry (LC-MS/MS) is an analytical technique that measures the mass-to-charge ratio of testosterone. To state it more simply, LC-MS/MS detects and measures testosterone using its physical properties, its molecular weight and unique fragmentation pattern. In this assay testosterone is extracted from the patient’s sample and analyzed by LC-MS/MS.
The high specificity of tandem mass spectrometry is enhanced by the measurement of two product ions of testosterone. This permits qualitative confirmation of the compound’s identity in every sample and elimination of potential interferences that can be found in immunoassays. This assay is able to measure very low levels of testosterone.
Selected References1. Manni A, Pardridge WM, Cefalu W, et al: Bioavailability of albumin-bound testosterone. J Clin Endocrinol Metab 1985;61:705 2. New MI, Josso N: Disorders of gonadal differentiation and congenital adrenal hyperplasia. Endocrinol Metab Clin North Am 1988;17:339-366 3. Dumesic DA: Hyperandrogenic anovulation: a new view of polycystic ovary syndrome. Postgrad Obstet Gynecol 1995 June;15(13) 4. Morley JE, Perry HM 3rd: Androgen deficiency in aging men: role of testosterone replacement therapy. J Lab Clin Med 2000;135:370-378 5. Ankarberg-Lindgren C, Norjavaara E. Estradiol in pediatric endocrinology. Am J Clin Pathol. 2009; 132 (6) :978-980. 6. Bloomfield D. Secondary amenorrhea. Pediatr Rev. 2006; 27 (3) :113-114. 7. Goswami D, Conway GS. Premature ovarian failure. Hum Reprod Update. 2005; 11 (4) :391-410. 8. Heiman DL. Amenorrhea. Prim Care. 2009; 36 (1) :1-17, vii. 9. Master-Hunter T, Heiman DL. Amenorrhea: evaluation and treatment. Am Fam Physician. 2006; 73 (8) :1374-1382. 10. Practice Committee of the American Society for Reproductive Medicine Current evaluation of amenorrhea. Fertil Steril. 2008; 90 (5 Suppl) :S219-S225. 11. Rebar RW. Premature ovarian failure. Obstet Gynecol. 2009; 113 (6) :1355-1363. 12. Rudolph LM. Cytogenetics of Infertility. In Gersen SL, Keagle MB, eds. The Principles of Clinical Cytogenetics. Totowa, New Jersey: Humana Press Inc, 2005. pp. 247-265. 13. Warren MP, Hagey AR. The genetics, diagnosis and treatment of amenorrhea. Minerva Ginecol. 2004; 56 (5) :437-455. 14. Wilson GR, Haddad JE, Haddad CJ. Amenorrhea: common causes and evaluation. Compr Ther. 2005; 31 (4) :270-278. 15. http://labtestsonline.org/
WHAT TEST FOR WHICH PATIENT POPULATION
MENIn general, assessing testosterone levels in adult men can be accurately and easily performed using immunoassays.
Free testosterone can be directly measured given the normal levels found in men or it can be calculated.
Bioavailable testosterone can be assessed by measuring the total testosterone, SHBG and albumin and then applying a mathematical formula to calculate the bioavailable testosterone.
In adult men who are expected to have very low levels of testosterone, the LC-MS/MS assay should be the method of choice. Men who fall into this group include those being treated for metastatic prostate cancer with gonadotropin-releasing hormone analogs and/or by anti-androgen therapy.
WOMEN AND CHILDRENAssessing testosterone levels in women and children can generally be more accurately done using LC-MS/MS.
Free testosterone can be calculated.
Bioavailable testosterone can be assessed by measuring the total testosterone, SHBG and albumin and then applying a mathematical formula to calculate the bioavailable testosterone.
TEST INFORMATION
For more information, please contact your local marketing representative.
OrderCode Test Name
Testosterone Measurement
MethodTesting
Population
TSTOTM Testosterone Total (Adult Males)
Immunoassay Adult Men YES NO NO NO NO
TSTFRMTestosterone,
Free (Adult Males)
Immunoassay Adult Men NO YES NO NO NO
TSTFMTestosteroneTotal & Free
(Adult Males)Immunoassay Adult Men YES YES NO NO NO
TESTFBTestosterone,
Total and Free + SHBG, Adult Male
Immunoassay Adult Men YES YES NO NO YES
TESTAMTestosterone
Total by LC-MS/MS
LC-MS/MSMen on Testosterone Supressing Therapy,
Women and Children. Also, Adult Men when LC-MS/MS is requested.
YES NO NO NO NO
TESFRF Testosterone, Free by LC-MS/MS
LC-MS/MSMen on Testosterone Supressing Therapy,
Women and Children. Also, Adult Men when LC-MS/MS is requested.
NO NO YES NO NO
TETFRF Testosterone Total & Free by LC-MS/MS
LC-MS/MS Men on Testosterone Supressing Therapy,
Women and Children. Also, Adult Men when LC-MS/MS is requested.
YES NO YES NO NO
TESAMBTestosterone
Total by LC-MS/MS, & Bioavailable + SHBG
LC-MS/MSMen on Testosterone Supressing Therapy,
Women and Children. Also, Adult Men when LC-MS/MS is requested.
YES NO YES YES YES
TESFCTestosterone
Total by LC-MS/MS (Females and Children)
LC-MS/MS Women and Children YES NO NO NO NO
TESFCB
Testosterone Total by LC-MS/MS, &
Bioavailable + SHBG (Females & Children)
LC-MS/MS Women and Children YES NO YES YES YES
Tota
l Te
stos
tero
neM
easu
red
Free
Te
stos
tero
neCa
lcul
ated
Fre
e Te
stos
tero
neBi
oava
ilabl
e Te
stos
tero
neS
HB
G
