Testosterone, Free, Equilibrium Ultrafiltration With Total Testosterone
Use
Evaluate hirsutism and masculinization in women; evaluate testicular function in clinical states where the testosterone binding proteins may be altered (obesity, cirrhosis, thyroid disorders)
Special Instructions
State patient's age and sex on the test request form.
Limitations
The concentration of free testosterone is very low, typically less than 2% of the total testosterone concentration. In most men and women, more than 50% of total circulating testosterone is bound to sex hormone-binding globulin (SHBG) and most of the rest is bound to albumin. Routinely available assay methods used to measure total testosterone are not sensitive enough to accurately quantitate the free testosterone fraction directly. An indirect method, equilibrium ultrafiltration, is used instead, where tritiated testosterone is added to the sample and allowed to come to equilibrium with testosterone in the serum at physiological temperature. The radioactivity of the protein-free ultrafiltrate is measured and used to calculate the percent free testosterone, then the concentration of free testosterone is calculated by multiplying by the total testosterone concentration.
Methodology
Immunoassay (ECLIA)
Biomarkers
LOINC Codes
- 58952-3
- 2986-8
- 2991-8
- 15432-8
Result Turnaround Time
2-4 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
2.50 mL
Minimum Volume
2 mL
Container
Red-top tube or gel-barrier tube
Collection Instructions
Separate serum from cells. If a red-top tube is used, transfer separated serum to a plastic transport tube.
Storage Instructions
Room temperature
Causes for Rejection
Hemolyzed sample; icteric sample; gross lipemia; recently administered isotopes; plasma specimen
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 14 days |
| Refrigerated | 14 days |
| Frozen | 14 days |