Testosterone, Total and Free, Serum
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
This assay is the alternative, second-level test for suspected increases or decreases in physiologically active testosterone (preferred: TTBS / Testosterone, Total and Bioavailable, Serum); indications:
-Assessment of androgen status in cases with suspected or known sex hormone-binding globulin-binding abnormalities
-Assessment of functional circulating testosterone in early pubertal boys and older men
-Assessment of functional circulating testosterone in women with symptoms or signs of hyperandrogenism, but normal total testosterone levels
-Monitoring of testosterone therapy or antiandrogen therapy in older men and in females
Profile Information A profile is a group of laboratory tests that are ordered and performed together under a single Mayo Test ID. Profile information lists the test performed, inclusive of the test fee, when a profile is ordered and includes reporting names and individual availability.
|Test ID||Reporting Name||Available Separately||Always Performed|
|FRTST||Testosterone, Free, S||No||Yes|
|TTST||Testosterone, Total, S||Yes, (Order TTST)||Yes|
FRTST: Equilibrium Dialysis
TTST: Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Testosterone, Total and Free, S
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Preferred: Red top
Acceptable: Serum gel
Specimen Volume: 2.5 mL
Additional Information: Patient's age and sex are required.
Forms: If not ordering electronically, submit a General Request Form (Supply T239) with the specimen.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Mild OK; Gross reject
Mild OK; Gross OK
Mild OK; Gross OK
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
|Serum||Refrigerated (preferred)||14 days|
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
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-stimulating 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 (TTBS / Testosterone, Total and Bioavailable, Serum) is the preferred assay.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
Males: 9-30 ng/dL
Females: 0.3-1.9 ng/dL
Reference values are not established for subjects <16 years.
0-5 months: 75-400 ng/dL
6 months-9 years: <7-20 ng/dL
10-11 years: <7-130 ng/dL
12-13 years: <7-800 ng/dL
14 years: <7-1,200 ng/dL
15-16 years: 100-1,200 ng/dL
17-18 years: 300-1,200 ng/dL
> or =19 years: 240-950 ng/dL
I (prepubertal): <7-20
V (young adult): 300-950
0-5 months: 20-80 ng/dL
6 months-9 years: <7-20 ng/dL
10-11 years: <7-44 ng/dL
12-16 years: <7-75 ng/dL
17-18 years: 20-75 ng/dL
> or =19 years: 8-60 ng/dL
I (prepubertal): <7-20
V (young adult): 12-60
*Puberty onset (transition from Tanner stage I to Tanner stage II) occurs for boys at a median age of 11.5 (+/-2) years and for girls at a median age of 10.5 (+/-2) years. There is evidence that it may occur up to 1 year earlier in obese girls and in African American girls. For boys, there is no definite proven relationship between puberty onset and body weight or ethnic origin. Progression through Tanner stages is variable. Tanner stage V (young adult) should be reached by age 18.
Total testosterone and general interpretation of testosterone abnormalities:
Decreased testosterone levels indicate partial or complete hypogonadism. Serum testosterone levels are usually below the reference range. The cause is either primary or secondary/tertiary (pituitary/hypothalamic) testicular failure.
Primary testicular failure is associated with increased luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels, and decreased total, bioavailable, and free testosterone levels. Causes include:
-Genetic causes (eg, Klinefelter syndrome, XXY males)
-Developmental causes (eg, testicular maldescent)
-Testicular trauma or ischemia (eg, testicular torsion, surgical mishap during hernia operations)
-Infections (eg, mumps)
-Autoimmune diseases (eg, autoimmune polyglandular endocrine failure)
-Metabolic disorders (eg, hemochromatosis, liver failure)
Secondary/tertiary hypogonadism, also known as hypogonadotrophic hypogonadism, shows low testosterone and low, or inappropriately "normal," LH/FSH levels; causes include:
-Inherited or developmental disorders of hypothalamus and pituitary (eg, Kallmann syndrome, congenital hypopituitarism)
-Pituitary or hypothalamic tumors
-Hyperprolactinemia of any cause
-Malnutrition or excessive exercise
-Medical or recreational drugs (eg, estrogens, GNRH analogs, cannabis)
Increased testosterone levels:
-In prepubertal boys, increased levels of testosterone are seen in precocious puberty. Further work-up is necessary to determine the cause(s) of precocious puberty.
-In adult men, testicular or adrenal tumors or androgen abuse might be suspected if testosterone levels exceed the upper limit of the normal range by more than 50%.
Monitoring of testosterone replacement therapy:
Aim of treatment is normalization of serum testosterone and LH. During treatment with depot-testosterone preparations, trough levels of serum testosterone should still be within the normal range, while peak levels should not be significantly above the normal young adult range.
Monitoring of antiandrogen therapy:
Aim is usually to suppress testosterone levels to castrate levels or below (no more than 25% of the lower reference range value).
Decreased testosterone levels may be observed in primary or secondary ovarian failure, analogous to the situation in men, alongside the more prominent changes in female hormone levels. Most women with oophorectomy have a significant decrease in testosterone levels.
Increased testosterone levels may be seen in:
-Congenital adrenal hyperplasia: nonclassical (mild) variants may not present in childhood but during or after puberty. In addition to testosterone, multiple other androgens or androgen precursors are elevated, such as 17OH-progesterone (OHPG / 17-Hydroxyprogesterone, Serum), often to a greater degree than testosterone.
-Prepubertal girls: analogous to males, but at lower levels, increased levels of testosterone are seen in precocious puberty.
-Ovarian or adrenal neoplasms: high estrogen values also may be observed, and LH and FSH are low or "normal." Testosterone-producing ovarian or adrenal neoplasms often produce total testosterone values >200 ng/dL.
-Polycystic ovarian syndrome: hirsutism, acne, menstrual disturbances, insulin resistance and, frequently, obesity, form part of this syndrome. Total testosterone levels may be normal or mildly elevated and uncommonly >200 ng/dL.
Monitoring of testosterone replacement therapy:
The efficacy of testosterone replacement in females is under study. If it is used, total testosterone levels should be kept within the normal female range at all times. Bioavailable or free testosterone levels also should be monitored to avoid over treatment.
Monitoring of antiandrogen therapy:
Antiandrogen therapy is most commonly employed in the management of mild-to-moderate "idiopathic" female hyperandrogenism, as seen in polycystic ovarian syndrome. Total testosterone levels are a relatively crude guideline for therapy and can be misleading. Therefore, bioavailable or free testosterone also should be monitored to ensure treatment adequacy. However, there are no universally agreed biochemical end points and the primary treatment end point is the clinical response.
Usually, bioavailable and free testosterone levels parallel the total testosterone levels. However, a number of conditions and medications are known to increase or decrease the sex hormone-binding globulin (SHBG) (SHBG / Sex Hormone Binding Globulin [SHBG], Serum) concentration, which may cause total testosterone concentration to change without necessarily influencing the bioavailable or free testosterone concentration, or vice versa:
-Treatment with corticosteroids and sex steroids (particularly oral conjugated estrogen) can result in changes in SHBG levels and availability of sex-steroid binding sites on SHBG. This may make diagnosis of subtle testosterone abnormalities difficult.
-Inherited abnormalities in SHBG binding
-Liver disease and severe systemic illness
-In pubertal boys and adult men, mild decreases of total testosterone without LH abnormalities can be associated with delayed puberty or mild hypogonadism. In this case, either bioavailable or free testosterone measurements are better indicators of mild hypogonadism than determination of total testosterone levels.
-In polycystic ovarian syndrome and related conditions, there is often significant insulin resistance, which is associated with low SHBG levels. Consequently, bioavailable or free testosterone levels may be more significantly elevated.
Either bioavailable (TTBS / Testosterone, Total and Bioavailable, Serum) or free (TGRP / Testosterone Total and Free, Serum) testosterone should be used as supplemental tests to total testosterone in the above situations. The correlation coefficient between bioavailable and free testosterone (by equilibrium dialysis) is 0.9606. However, bioavailable testosterone is usually the preferred test, as it more closely reflects total bioactive testosterone, particularly in older men. Older men not only have elevated SHBG levels, but albumin levels also may vary due to coexisting illnesses.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Early-morning testosterone levels in young male individuals are, on average, 50% higher than p.m. levels. Our reference ranges have been derived from a.m. specimens.
Testosterone levels can fluctuate substantially between different days, and sometimes even more rapidly. Assessment of androgen status should be based on more than a single measurement.
The low end of the normal reference range for total testosterone in prepubertal subjects is not yet established.
While free testosterone can be used for the same indications as bioavailable testosterone, determination of bioavailable testosterone levels may be superior to free testosterone measurement in most situations.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Manni A, Pardridge WM, Cefalu W, et al: Bioavailability of albumin-bound testosterone. J Clin Endocrinol Metab 1985;61:705
2. New MI, Josso N: Disorders of gonadal differentiation and congenital adrenal hyperplasia. Endocrinol Metab Clin North Am 1988;17:339-366
3. Dumesic DA: Hyperandrogenic anovulation: a new view of polycystic ovary syndrome. Postgrad Obstet Gynecol 1995 June;15(13)
4. Morley JE, Perry HM 3rd: Androgen deficiency in aging men: role of testosterone replacement therapy. J Lab Clin Med 2000;135:370-378
Method Description Describes how the test is performed and provides a method-specific reference
This method utilizes a radioactive tracer together with equilibrium dialysis to analyze and determine the host’s serum binding capacity for testosterone. During buffered dialysis, any testosterone that is unbound to sex hormone binding-globulin (SHBG) or albumin is free to pass through the semipermeable dialysis tubing, while those testosterone molecules bound to the binding proteins will be held inside the tubing. After dialysis, radioactivity is measured from a sample of the dialysate buffer; the resulting counts are compared to known values to yield a result expressed as a percentage of total testosterone. To yield an absolute free testosterone, the calculated percentage is multiplied by the total testosterone concentration as determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS).(Unpublished Mayo method)
Deuterated stable isotope (d3-testosterone) is added to a 0.2-mL serum sample as an internal standard. Protein is precipitated from the mixture by the addition of acetonitrile. The testosterone and internal standard are extracted from the resulting supernatant by an online extraction utilizing high-throughput liquid chromatography (HTLC). This is followed by conventional liquid chromatography and analysis on a tandem mass spectrometer equipped with a heated nebulizer ion source.(Wang C, Catlin DH, Demers LM, et al: Measurement of total testosterone in adult men: comparison of current laboratory methods versus liquid chromatography-tandem mass spectrometry. J Clin Endocrinol Metab 2004;89:534-543; Taieb J, Mathian B, Millot F, et al: Testosterone measured by 10 immunoassays and by isotope-dilution gas chromatography-mass spectrometry in sera from 116 men, women, and children. Clin Chem 2003;49:1381-1395)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Friday; 2 p.m. Saturday and Sunday; Varies
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
See Individual Unit Codes
Performing Laboratory Location The location of the laboratory that performs the test
CPT Code Information Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
|Result ID||Reporting Name||LOINC Code|
|3631||Testosterone, Free, S||2991-8|
|8533||Testosterone, Total, S||2986-8|