Testosterone, Free, Bioavailable and Total, Males (Adult), Immunoassay Blood Test
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| Feature |
Labcorp
|
Quest Diagnostics
|
|---|---|---|
| Price | Coming soon | $48.49 |
| Results in | — | ~5 business days |
| Sample type | — | Blood Serum |
| Require fasting | — | No |
About the test
This test panel may be helpful in assessing androgen status and screening for hypogonadism in men. This immunoassay cannot accurately measure the low testosterone levels generally found in women, children, and men with hypogonadism [1].
Testosterone circulates in 3 major forms: unbound (free), weakly bound to albumin, and tightly bound to sex hormone-binding globulin (SHBG). Free testosterone comprises 2% to 4% of total testosterone and is biologically active. Albumin-bound testosterone can dissociate from albumin in capillaries and become available to tissue. Thus, bioavailable testosterone refers to free testosterone plus albumin-bound testosterone. In this panel, free testosterone and bioavailable testosterone concentrations are calculated based on measurements of total T, SHBG, and albumin.
In men, fasting total testosterone concentrations measured in the morning are recommended for screening for hypogonadism [2]. In patients with conditions affecting SHBG concentrations or when total testosterone levels are near the lower limit, free testosterone levels may be more sensitive than total testosterone levels for assessing androgen status. When the total testosterone level is low, or the total testosterone level is normal but free testosterone is low, the fasting total testosterone should be confirmed on another morning [2]. This test may also be used to monitor testosterone replacement therapy.
Direct immunoassays cannot accurately quantify low concentrations of testosterone, especially concentrations under the lower limit of the normal range for men [1]. Chromatography/mass spectrometry is preferred for quantifying testosterone levels in children, women, or men with low testosterone levels [1]. Further studies are needed to elaborate the use of bioavailable testosterone concentrations.
Note: Dietary supplements containing biotin may interfere with this assay. Please refer to the collection instructions for more information.
The results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings.
References
- Rosner W, et al. J Clin Endocrinol Metab. 2007;92(2):405-413.
- Bhasin S, et al. J Clin Endocrinol Metab. 2018;103(5):1715-1744.
Included biomarkers & Reference ranges
| Biomarker | Reference range |
|---|---|
| Albumin The main protein made by your liver, which helps balance fluids and carries hormones, vitamins, and medications through your blood. Low levels can point to liver, kidney, or nutrition issues. | 3.6–5.1 g/dL |
| Bioavailable Testosterone The portion of your testosterone that's either free or loosely bound to albumin — the amount actually usable by your body's tissues. | — |
| Free Testosterone The small portion of your testosterone that's unbound and biologically active, considered a more accurate reflection of usable hormone than total testosterone. | — |
| Sex Hormone-Binding Globulin (SHBG) A protein that binds and transports testosterone and estrogen in your blood, determining how much hormone is 'free' and active. Important for interpreting sex hormone results. | M 10–50 nmol/L F 17–124 nmol/L |
| Testosterone The primary male sex hormone, also present in women in smaller amounts. Evaluated for low testosterone symptoms, fertility, and reproductive hormone imbalances. | M 250–1100 ng/dL F 2–45 ng/dL |
Reference ranges vary by lab, age, and sex (M/F). Your report shows your exact range. Click any biomarker to see its optimal range and what your results mean.
Preparation
- Dietary supplements containing biotin may interfere in assays and may skew results to be either falsely high or falsely low. For patients receiving the recommended daily doses of biotin, draw samples at least 8 hours following the last biotin supplementation. For patients on mega-doses of biotin supplements, draw samples at least 72 hours following the last biotin supplementation.
How it works
- 1. Order online No referral or insurance
- 2. Get a requisition By email in 24–72 hours
- 3. Visit a draw center Bring a matching photo ID
- 4. Get results Securely by email
- These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
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