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Test Code:
TESTF

Order Name:
Free Testosterone

 
Useful For:
Second- or third-order test for evaluating testosterone status (eg, when abnormalities of sex hormone-binding globulin are present)
 
Methodology:
See details from individual unit test
 
Test List In Profile:
Total Testosterone
SHBG
Albumin
 
AliasesName:
Bioavailable Testosterone
 
 
 
Test Code:
TESTF

Order Name:
Free Testosterone

 
Collection Specimen Or Container:
Blood/ Plain Blood (Red Top) 6 mL, 1 tube
 
Specimen Testing Type:
Serum, minimum volume 2 mL
 
Sub Mission Container:
Plastic vial
 
Rejection Criteria:
See details from individual unit test
 
Specimen Stabillity:
See details from individual unit test
 
 
 
Test Code:
TESTF

Order Name:
Free Testosterone

 
Schedule:
Tested daily until 8:00 p.m.
 
Turnaround Time:
Specimen collected to reported within 1 day
 
Performing Location:
Immunology, Laboratory Department Tel. 13227
 
Specimen Retention Time:
5 days
 
 
 
Test Code:
TESTF

Order Name:
Free Testosterone

 
 
Clinical Information:
Testosterone is the major androgenic hormone. It is responsible for the development of the male external genitalia and secondary sexual characteristics. In females, its main role is as an estrogen precursor. In both genders, it also exerts anabolic effects and influences behavior.

In men, testosterone is secreted by the testicular Leydig cells and, to a minor extent, by the adrenal cortex. In premenopausal women, the ovaries are the main source of testosterone with minor contributions by the adrenals and peripheral tissues. After menopause, ovarian testosterone production is significantly diminished. Testosterone production in testes and ovaries is regulated via pituitary-gonadal feedback involving luteinizing hormone (LH) and, to a lesser degree, inhibins and activins.

Most circulating testosterone is bound to sex hormone-binding globulin (SHBG), which in men also is called testosterone-binding globulin. A lesser fraction is albumin bound and a small proportion exists as free hormone. Historically, only the free testosterone was thought to be the biologically active component. However, testosterone is weakly bound to serum albumin and dissociates freely in the capillary bed, thereby becoming readily available for tissue uptake. All non-SHBG-bound testosterone is therefore considered bioavailable.

During childhood, excessive production of testosterone induces premature puberty in boys and masculinization in girls. In adult women, excess testosterone production results in varying degrees of virilization, including hirsutism, acne, oligo-amenorrhea, or infertility. Mild-to-moderate testosterone elevations are usually asymptomatic in males, but can cause distressing symptoms in females. The exact causes for mild-to-moderate elevations in testosterone often remain obscure. Common causes of pronounced elevations of testosterone include genetic conditions (eg, congenital adrenal hyperplasia); adrenal, testicular, and ovarian tumors; and abuse of testosterone or gonadotrophins by athletes.

Decreased testosterone in females causes subtle symptoms. These may include some decline in libido and nonspecific mood changes. In males, it results in partial or complete degrees of hypogonadism. This is characterized by changes in male secondary sexual characteristics and reproductive function. The cause is either primary or secondary/tertiary (pituitary/hypothalamic) testicular failure. In adult men, there also is a gradual modest, but progressive, decline in testosterone production starting between the fourth and sixth decades of life. Since this is associated with a simultaneous increase of SHBG levels, bioavailable testosterone may decline more significantly than apparent total testosterone, causing nonspecific symptoms similar to those observed in testosterone deficient females. However, severe hypogonadism, consequent to aging alone, is rare.

Measurement of total testosterone (TTST / Testosterone, Total, Serum) is often sufficient for diagnosis, particularly if it is combined with measurements of LH and follicle-stimulation hormone (FSH) (LH / Luteinizing Hormone [LH], Serum and FSH / Follicle-Stimulating Hormone [FSH], Serum). However, these tests may be insufficient for diagnosis of mild abnormalities of testosterone homeostasis, particularly if abnormalities in SHBG (SHBG / Sex Hormone Binding Globulin [SHBG], Serum) function or levels are present. Additional measurements of free testosterone or bioavailable testosterone are recommended in this situation; bioavailable testosterone (see TTBS / Testosterone, Total and Bioavailable, Serum) is the preferred assay.
 
Reference Value:
See details from individual unit test
 
Clinical Reference:
https://www.mayocliniclabs.com (Retrieved: Feb 2020)