Testosterone, Free, Mass Spectrometry/Equilibrium Dialysis (Endocrine Sciences)
Use
Free testosterone is the fraction of total testosterone that is not bound to circulating proteins. The free fraction is available to diffuse into target cells to interact with receptors or enzymes. The concentration of free testosterone is low relative to total testosterone, typically <3% of the total testosterone concentration. Total circulating testosterone is bound to sex hormone-binding globulin (SHBG) or albumin. Measurement of total and free testosterone is key in diagnosis of androgen excess or deficiency. Free testosterone is best measured by equilibrium dialysis, while total testosterone is measured by HPLC with tandem mass spectrometry.1-3 Free testosterone is estimated in this profile using these recommended techniques.
Special Instructions
This method is recommended for testing women, children, and hypogonadal men. Ensure serum is separated from cells within 45 minutes of venipuncture and send serum in a plastic transport tube. For multiple tests, separate frozen specimens should be submitted to avoid delays.
Limitations
The method is specifically recommended for women, children, and hypogonadal men, and it may not be suitable for other populations. It is crucial that the samples are handled as advised to prevent deterioration, affecting the accuracy of the results due to degradation or changes in the specimen during handling or storage.
Methodology
Mass Spectrometry
Biomarkers
LOINC Codes
- 2991-8
- 2986-8
- 15432-8
- 2991-8
Result Turnaround Time
6-10 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
2 mL
Minimum Volume
1 mL
Container
Gel-barrier tube or red-top tube
Collection Instructions
Serum must be separated from cells within 45 minutes of venipuncture. Send serum in a plastic transport tube. Submit separate frozen specimens for each test requested to avoid delays.
Storage Instructions
Freeze
Causes for Rejection
EDTA plasma; citrated plasma; hemolysis >5%
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 6 days |
| Refrigerated | 7 days |
| Frozen | 2.6 years |