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Testosterone, Bioavailable

Source Blood
Mnemonic

BIOTESTO

If Measured Bioavailable Testosterone is requested, refer to Testosterone, Measured Bioavailable.

Specimen Requirements

This is a user pay test not covered by Alberta Health & Wellness. The patient must pay $50.00 at time of collection.

1 x 3.5 mL gold top SST tube AND 1 x 3.0 mL light green (mint) top PST tube

1 mL serum AND 0.5 mL plasma

Specimen Handling  
Additional Information The concentration of Bioavailable Testosterone is derived from a mathematical expression based on constants for the binding of Testosterone to Sex Hormone Binding Globulin and Albumin.

Indicate gender of patient on the requisition.

Testosterone exhibits diurnal variation in adult males. Values are highest in the morning, with decreases up to 25% later in the day. Reference intervals were established on specimens collected in the morning (07:00 - 10:00), thus it is suggested to collect specimens within this timeframe. The amplitude of diurnal variation decreases with age, with patients aged >70 showing an approximate 10% decrease.
Diurnal variation of testosterone in females is not well defined in the literature, but similar variation may be expected in pre-menopausal women.
Reference:
Brambilla, DJ, Matsumoto, AM, Araujo, AB, McKinlay, JB. The Effect of Diurnal Variation on Clinical Measurement of Serum Testosterone and Other Sex Hormone Levels in Men. J. Clin. Endocrinol. Metab. 2009. 94(3):907-913.
Testing Location Immunochemistry
Testing Frequency Weekdays
Alternate Name(s) Bioavailable Testosterone
Reference Interval

Adult male

4.0-16.0 nmol/L

Adult female

0.1-1.0 nmol/L