Testosterone Free, Profile II
Also known as: Free Testosterone by Vermeulen Equation, Free Testosterone, Calculated
Use
Free testosterone is the concentration of unbound testosterone in serum.1 The majority (approximately 60% to 90%) of serum total testosterone is associated with sex hormone binding globulin (SHBG); this fraction is tightly bound and biologically unavailable to its target tissues. The remaining bioavailable testosterone is mostly bound to albumin, with only a small fraction (approximately 0.5% to 2%) circulating in the free form.1,2 Free testosterone is the form of testosterone that can diffuse into the tissues and act on receptors and is considered the active fraction by many physicians.1,3,4 Free testosterone assessment is recommended as a primary or secondary measure of androgen activity in men2,5-11 and women.12-16 The equilibrium dialysis or ultrafiltration methods are recommended, however they are relatively difficult and expensive to perform. All of these methods are currently available from LabCorp.
Special Instructions
Not provided.
Limitations
The method of calculation for free testosterone is based on the Vermeulen equation, which calculates serum free testosterone concentrations based on association constants of testosterone, SHBG, and albumin, aligning with equilibrium kinetics. The test uses assays that are reliable, yet it is not cleared or approved by the FDA. Some circumstances may necessitate additional confirmatory or reflex tests, possibly extending the turnaround time.
Methodology
Mass Spectrometry
Biomarkers
LOINC Codes
- 58952-3 - Testost free+total panel SerPl-mCnc
- 1751-7 - Albumin SerPl-mCnc
- 2986-8 - Testost SerPl-mCnc
- 13967-5 - SHBG SerPl-sCnc
- 2991-8 - Testost Free SerPl-mCnc
Result Turnaround Time
4-6 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
2.8 mL
Minimum Volume
2 mL
Container
Red-top tube or gel-barrier tube
Collection Instructions
Serum should be transferred from cells within one hour of collection and transferred to a plastic transport tube.
Storage Instructions
Room temperature
Causes for Rejection
See individual test components.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 7 days |
| Refrigerated | 7 days |
| Frozen | 14 days |
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