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Test Name:
Testosterone, Free, Adult Males
- SBMF No:
30102 - Performance Lab Name:
Immunochemistry - Test Mnemonic:
TEST FREE - ABN:
Not required - CPT Code:
84402 - LOINC Code:
2991-8 - Also Known As:
Free Testosterone - Also See:
45752 Testosterone, Free, Females or Children - Spec Type:
Serum - Spec Container:
Gold top (SST) or red top (serum) tube - Pref Vol:
1.0 mL - Min Vol:
0.5 mL - Fasting:
No - Patient Prep:
Patient must not have received isotopes during 24-hour period prior to sample collection - Spec Collect:
Routine venipuncture - Spec Process:
Clot 30 minutes
Promptly centrifuge 15 minutes
Immediately transfer serum to separate plastic tube and refrigerate
If specimen will not be received at SBMF within 48 hours of collection, freeze - Spec Store Transport:
Refrigerated (48 hours) or frozen - Spec Stability:
48 hours refrigerated (2-8°C)
1 month frozen (-20°C); if will not be received by SBMF within 48 hours of collection, freeze - Spec Reject:
Severely lipemic sample - Methodology:
Radioimmunoassay (RIA) - Use:
Initially utilized to diagnose hypogonadism in males and frank hyperandrogenism in females
Not sensitive enough to reliably measure into the "androgen deficient" female range or the pediatric range - Clinical Significance:
Androgen deficiency in women is increasingly recognized as a new clinical syndrome, which has raised the awareness of importance of accurate and sensitive measurements of free testosterone levels in serum. Initially utilized to diagnose hypogonadism in males and frank hyperandrogenism in females, direct free testosterone measurement by RIA is no longer sensitive enough to reliably measure into the "androgen deficient" female range as well as pediatric range.
Testosterone circulates in plasma either in free form or bound to plasma proteins. The binding proteins include the specific sex hormone binding globulin (SHBG) and nonspecific proteins like albumin. Historically, only the free form of testosterone wasthought to be biologically active. However, some testosterone that is nonspecifically and weakly bound to albumin can be dissociated freely becoming available for tissue uptake through the capillary bed. Free and the albumin-bound testosterone levels are considered to be "bioavailable" and biologically activeBlood testosterone levels depend on rates of production, interconversion, metabolic clearance, and binding protein concentrations. Medications, various disease states, age, and some hormones can alter SHBG levels; therefore, concentrations of bioavailable testosterone more accurately reflect bioactive levels of testosterone than the measurement of total testosterone.
- Reference Range:
Male:
19-38 years: 8.8-27.0 pg/mL
39-59 years: 7.2-23.0 pg/mL
> 59 years: 5.6-19.0 pg/mL - Day Run:
Mon, Wed, Fri - Time Run:
8:00 am - Time Reported:
3:30 pm - Test Type:
HORMONE
