Test Catalog

Test Id : FFTST

Testosterone, Free and Weakly Bound, With Total Testosterone, LC/MS-MS

Useful For
Suggests clinical disorders or settings where the test may be helpful

 

Free and weakly bound testosterone (FWBT), also referred to as bioavailable testosterone, is thought to reflect an individual's biologically active, circulating testosterone. FWBT includes free testosterone and testosterone that is bound to albumin. FWBT does not include sex hormone-binding globulin-bound testosterone. The SHBG-bound fraction is biologically inactive because of the high binding affinity of SHBG for testosterone. The rapid dissociation of weakly bound testosterone from albumin results in the availability of essentially all albumin-bound testosterone for steroid-receptor interaction.

Method Name
A short description of the method used to perform the test

Ammonium sulfate precipitation; liquid chromatography/tandem mass spectrometry (LC/MS-MS)

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.

Yes

Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Testosterone,F/WklyBd+T LC/MS

Specimen Type
Describes the specimen type validated for testing

Serum

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Specimen Type: Serum

Container/Tube: Red or SST

Specimen Volume: 2 mL

Collection Instructions: Draw blood in a plain red-top tube(s), serum gel tube(s) is acceptable. Spin down and send 2 mL serum in a plastic, screw-capped vial, shipped refrigerated.

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

1.4 mL (does not allow for repeat testing)

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross Hemolysis Reject
Gross Lipemia Reject
Gross Icterus NA
Other NA

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 7 days
Ambient 7 days

Useful For
Suggests clinical disorders or settings where the test may be helpful

 

Free and weakly bound testosterone (FWBT), also referred to as bioavailable testosterone, is thought to reflect an individual's biologically active, circulating testosterone. FWBT includes free testosterone and testosterone that is bound to albumin. FWBT does not include sex hormone-binding globulin-bound testosterone. The SHBG-bound fraction is biologically inactive because of the high binding affinity of SHBG for testosterone. The rapid dissociation of weakly bound testosterone from albumin results in the availability of essentially all albumin-bound testosterone for steroid-receptor interaction.

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Free and weakly bound (bioavailable) testosterone measurement involves the selective precipitation of SHBG with ammonium sulfate. Tritiated testosterone is added to serum, which is then allowed to come to equilibrium at physiologic temperature. Testosterone bound to SHBG is then selectively precipitated with 50% ammonium sulfate, leaving free and albumin-bound testosterone in solution. The percentage of tritiated label not bound to SHBG is multiplied by the total testosterone to produce bioavailable testosterone.

 

Elevated levels of FWBT are observed in female hirsutism. The measurement of free and weakly bound testosterone in women, when used in conjunction with the assay of the DHEA-S and SHBG, can be used to establish etiology of hirsutism. In males, decreased serum concentrations are associated with hypogonadism. FWBT levels tend to increase during pregnancy but have been found to remain below the upper limit of the reference interval. Total testosterone levels in women decrease by approximately 30% after menopause. Administration of exogenous estrogens has the physiologic effect of increasing SHBG concentrations and suppressing the production of androgens by the ovary. This results in a net decrease of FWBT. Decreased FWBT levels have been associated with diminished libido and loss of bone density. FWBT levels in males fall with age at a rate that exceeds that of total testosterone and parallels the drop in DHEA sulfate. This decrease is though to be caused by diminished testicular production and not due to hypothalamic/pituitary insufficiency. Decreased FWBT was not, however, found to correlate with diminished potency. Since SHBG has been found to increase with age, the FWBT level may be a more reliable indicator of testosterone production that total testosterone.

Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

CHILDREN

 

 

Male Range (ng/dL)

Female Range (ng/dL)

Premature Infants

 

 

26 to 28 weeks, Day 4

59.0-125.0

5.0-16.0

31 to 35 Weeks, Day 4

37.0-198.0

5.0-22.0

 

Full-term Infants

Newborns

75.0-400.0

20.0-64.0

Males 1 to 7 Months

Levels decrease rapidly the first week to 20.0-50.0 ng/dL, then increase to 60.0-400.0 ng/dL (mean=190.0) between 20-60 days. Levels then decline to prepubertal range of <2.5-10.0 by seven months.

Females 1 to 7 Months

Levels decrease during the first month to <10.0 ng/dL and remain there until puberty.

 

Prepubertal Children

1 to 10 Years

1 to 9 Years

 

<2.5-10.0

<2.5-10.0

 

PUBERTY

 

Tanner Stage

Age (Years)

Range (ng/dL)

Mean (ng/dL)

Males

 

 

 

1

<9.8

<2.5-10.0

4.9

2

9.8-14.5

18.0-150.0

42.0

3

10.7-15.4

100.0-320.0

190.0

4

11.8-16.2

200.0-620.0

372.0

5

12.8-17.3

350.0-970.0

546.0

 

Tanner Stage

Age (Years)

Range (ng/dL)

Mean (ng/dL)

Females

 

 

 

1

<9.2

<2.5-10.0

4.9

2

9.2-13.7

7.0-28.0

18.0

3

10.0-14.4

15.0-35.0

25.0

4

10.7-15.6

13.0-32.0

22.0

5

11.8-18.6

20.0-38.0

28.0

 

ADULTS

 >or=18 Years

Range (ng/dL)

Males

350.0-1030.0

Females

Premenopausal

Postmenopausal

 

10.0-55.0

7.0-40.0

 

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Pardridge WM. Transport of protein-bound hormones into tissues in vivo. Endocr Rev. 1981; 2(1):103-123 (review). PubMed 7028469

2. Cumming DC, Wall SR. Nonsex hormone-binding globulin-bound testosterone as a marker for hyperandrogenism. J Clin Metabol. 1985; 61(5):873-876. PubMed 4044776

3. Kerlan V, Nahoul K, Le Martelot MT, et al. Longitudinal study of maternal plasma bioavailable testosterone and androstanediol glucuronide levels during pregnancy. Clin Endocrinol (Oxf). 1994; 40(2):263-267. PubMed 8137527

4. Davis SR, Burger HG. Use of androgens in postmenopausal women. Curr Opin Obstet Gynecol. 1997; 9(3):177-180 (review). PubMed 9263701

5. Jassal SK, Barret-Connor E, Edelstein SL. Low bioavailable testosterone levels predict future height loss in postmenopausal women. J Bone Miner Res. 1995; 10(4):650-654. PubMed 7610937

6. Morley JE, Kaiser F, Raum WJ, et al. Potentially predictive and manipulable blood serum correlates of aging in the healthy male: Progressive decreases in bioavailable testosterone, dehydroepiandrosterone sulfate, and the ratio of insulin-like growth factor 1 to growth hormone. Proc Natl Acad Sci USA. 1997; 94(14):7537-7542. PubMed 9207127

7. Nahoul K, Roger M. Age-related decline of plasma bioavailable testosterone in adult men. J Steroid Biochem Mol Biol. 1990; 35(2):293-299. PubMed 2106599

8. Korenman SG, Morley JE, Mooradian AD, et al. Secondary hypogonadism in older men: Its relation to impotence. J Clin Endocrinol Metab. 1990; 71(4):963-969. PubMed 2205629

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information

No

Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Daily 1st and 3rd shifts

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

6 to 10 days

Performing Laboratory Location
Indicates the location of the laboratory that performs the test

LabCorp Burlington

Fees
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LOINC® Information

Test Id Test Order Name Order LOINC Value
FFTST Testosterone,F/WklyBd+T LC/MS Not Provided
Result Id Test Result Name Result LOINC Value
Result LOINC Value Tooltip
Z6079 Testosterone, Total, LC/MS 2986-8
Z6080 Testost. % Free+Weakly Bound 6891-6
Z6081 Testost. F+W Bound 2990-0

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports