Testosterone: Total, Free & Bioavailable

Performing Lab: Central Lab

4783

Sunquest: TFBAT

Sex hormone binding globulin (SBG); Total testosterone (TSTTO); Free testosterone (TSTFR); Bioavailable testosterone (TSTBA)

1.0 mL Serum Separator (gold-top) tube

0.4 mL

Refrigerated

Refrigerated: 5 days

Plasma is not an acceptable specimen type. Hemolysis, Lipemia

Monday - Friday

Same Day

Analyte Gender Age Reference Range SHBG Female 20-46 Years 18-136 nmol/L SHBG Female 47-91 Years 17-125 nmol/L SHBG Male 20-69 Years 16-70 nmol/L Testosterone Total Female 20-46 Years 17-88 ng/dl Testosterone Total Female 47-91 Years 10-66 ng/dl Testosterone Total Male 20-69 Years 200-745 ng/dl Testosterone Free Female 20-46 Years 0.2-1.6 ng/dl Testosterone Free Female 47-91 Years 0.1-1.0 ng/dl Testosterone Free Male 20-69 Years 3.1-12.8 ng/dl Testosterone Bioavailable Female 20-46 years 3.7-37.5 ng/dl Testosterone Bioavailable Female 47-91 years 1.4-22.0 ng/dl Testosterone Bioavailable Male 20-69 years 71.7-300.0 ng/dl

See indivudal tests for reference range

Most circulating testosterone is bound to sex hormone-binding globulin (SHBG). Sex hormone-binding globulin (SHBG) is responsible for transport of testosterone and estradiol. Less than 2% of biologically active sex hormones are free in circulation with the remainder being bound with high affinity to SHBG and low affinity to albumin. Free sex hormones and those weakly bound to albumin are available to the tissues. The sum of these fractions represents the “bioavailable” hormone.

Androgen status assessment in various conditions requires more information than total testosterone measurements alone. Albumin, SHBG and total testosterone can be measured and used to calculate “free” and “bioavailable” testosterone to provide a better evaluation of androgen status.