Ulta Lab Tests

Testosterone, Free, Bioavailable and Total, Males (Adult), Immunoassay

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The following is a list of what is included in the item above. Click the test(s) below to view what biomarkers are measured along with an explanation of what the biomarker is measuring.

Albumin

Albumin is a protein made by the liver. A serum albumin test measures the amount of this protein in the clear liquid portion of the blood.

Sex Hormone Binding

The sex hormone binding globulin (SHBG) test measures the concentration of SHBG in the blood. SHBG is a protein that is produced by the liver and binds tightly to testosterone, dihydrotestosterone (DHT), and estradiol (an estrogen). In this bound state, it transports them in the blood as an inactive form. The amount of SHBG in circulation is affected by age and sex, by decreased or increased testosterone or estrogen production and can be affected by certain diseases and conditions such as liver disease, hyperthyroidism or hypothyroidism, and obesity. Changes in SHBG levels can affect the amount of testosterone that is available to be used by the body's tissues. A total testosterone test does not distinguish between bound and unbound testosterone but determines the overall quantity of testosterone. If a person's SHBG level is not normal, then the total testosterone may not be an accurate representation of the amount of testosterone that is available to the person's tissues.

TESTOSTERONE, FREE

TESTOSTERONE,BIOAVAILABLE

TESTOSTERONE,TOTAL,MALES

A testosterone test measures the amount of the male hormone, testosterone, in the blood. Both men and women produce this hormone. In males, the testicles produce most of the testosterone in the body. Levels are most often checked to evaluate signs of low testosterone: In boys -- early or late puberty and in men -- impotence, low level of sexual interest, infertility, thinning of the bones In females, the ovaries produce most of the testosterone and levels are most often checked to evaluate signs of higher testosterone levels, such as: decreased breast size, excess hair growth, increased size of the clitoris. irregular or absent menstrual periods and male-pattern baldness or hair thinning.
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The Testosterone, Free, Bioavailable and Total, Males (Adult), Immunoassay test contains 1 test with 5 biomarkers .

Clinical Significance

Testosterone, Free, Bioavailable and Total, Males (Adult), Immunoassay -

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
1. Rosner W, et al. J Clin Endocrinol Metab. 2007;92(2):405-413.
2. Bhasin S, et al. J Clin Endocrinol Metab. 2018;103(5):1715-1744.

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