FREE TESTOSTERONE BY RIA

Code
900.3730
Name
FREE TESTOSTERONE BY RIA
Category
None
Department
Send-Out
Start Date
Expiration Date
Synonyms
CPT Codes
84402
Site
SBMF
Reference Test
30102
ATLAS Test Code

Specimen Information

Type

Gold, SST

Volume

1.0 ml

Transport Info

Centrifuge and immediately transfer serum to separate plastic tube
Refrigerated 48 Hours
If specimen will not be received within 48 hours of collection, freeze serum and transport frozen

Fasting Required?
False
Patient Instructions

Patient must not have received isotopes during 24-hour period prior to sample collection

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

Methodology

Radioimmunoassay (RIA)

Clinical Significance

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
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.

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