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23318 Bioavailable Testosterone, Total and Free (TTFB)

Bioavailable Testosterone, Total and Free (TTFB)
Test Code: BIOTESO
Synonyms/Keywords
​Androgens, Bioavailable Testosterone, NonSex Hormone Binding Globulin (SHBG), Testosterone (ORDER 8533 if not specified), Testosterone Group (ORDER 8508), Testosterone, Total Only, Serum
Useful For
Second- or third– order test for evaluating testosterone status (eg, when abnormalities of sex hormone-binding globulin are present)​
Specimen Requirements
Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)		 Pediatric Minimum Volume
(no repeat)
Serum​ ​Red Top Tube (RTT) ​3.5 mL ​2 mL ​
Collection Processing Instructions
Patient's age and sex are required.​
Specimen Stability Information
Specimen Type Temperature Time
​Serum ​ ​Refrigerated (preferred) ​14 days
​Frozen 60 days
Rejection Criteria
Gross hemolysis
​Gross lipemia
​Gross icterus ​
Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
​Mayo Medical Laboratories
Testosterone, bioavailable: Monday through Friday
Testosterone, free: Monday through Saturday
Testosterone, total: Monday through Saturday​
Testosterone, bioavailable: 2 days
Testosterone, free: 3 days
Testosterone, total: 2 days​
Testosterone, bioavailable:: Differential Precipitation
Testosterone, free: Equilibrium Dialysis
Testosterone, total:: Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Reference Lab
Mayo Clinic Laboratories
Test 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 is often sufficient for diagnosis, particularly if it is combined with measurements of LH and follicle-stimulation hormone (FSH).  However, these tests may be insufficient for diagnosis of mild abnormalities of testosterone homeostasis, particularly if abnormalities in SHBG  function or levels are present.  Additional measurements of free testosterone or bioavailable testosterone are recommended in this situation; bioavailable testosterone is the preferred assay.
Reference Range Information
TESTOSTERONE, TOTAL
Males        
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      
Tanner Stages*                            
I (prepubertal): <7-20
II: 8-66
III: 26-800
IV: 85-1,200      
V (young adult): 300-950
 
Females           
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
Tanner Stages*
I (prepubertal): <7-20
II: <7-47
III: 17-75
IV: 20-75
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.
 
TESTOSTERONE, FREE
Males (adult):
20 - <25 years: 5.25-20.7 ng/dL
25 - <30 years: 5.05-19.8 ng/dL
30 - <35 years: 4.85-19.0 ng/dL
35 - <40 years: 4.65-18.1 ng/dL
40 - <45 years: 4.46-17.1 ng/dL
45 - <50 years: 4.26-16.4 ng/dL
50 - <55 years: 4.06-15.6 ng/dL
55 - <60 years: 3.87-14.7 ng/dL
60 - <65 years: 3.67-13.9 ng/dL
65 - <70 years: 3.47-13.0 ng/dL
70 - <75 years: 3.28-12.2 ng/dL
75 - <80 years: 3.08-11.3 ng/dL
80 - <85 years: 2.88-10.5 ng/dL
85 - <90 years: 2.69-9.61 ng/dL
90 - <95 years: 2.49-8.76 ng/dL
95 - 100+ years: 2.29-7.91 ng/dL
 
Males (children):
<1 year: Term infants
1 to 15 days: 0.20-3.10 ng/dL*
16 days to 1 year: Values decrease gradually from newborn (0.20-3.10 ng/dL) to prepubertal levels
1-8 years <0.04-0.11 ng/dL
9 years: <0.04-0.45 ng/dL
10 years: <0.04-1.26 ng/dL
11 years: <0.04-5.52 ng/dL
12 years: <0.04-9.28 ng/dL
13 years: <0.04-12.6 ng/dL
14 years: 0.48-15.3 ng/dL
15 years: 1.62-17.7 ng/dL
16 years: 2.93-19.5 ng/dL
17 years: 4.28-20.9 ng/dL
18 years: 5.40-21.8 ng/dL
19 years: 5.36-21.2 ng/dL
 
Females (adult):
20 - <25 years: 0.06-1.08 ng/dL
25 - <30 years: 0.06-1.06 ng/dL
30 - <35 years: 0.06-1.03 ng/dL
35 - <40 years: 0.06-1.00 ng/dL
40 - <45 years: 0.06-0.98 ng/dL
45 - <50 years: 0.06-0.95 ng/dL
50 - <55 years: 0.06-0.92 ng/dL
55 - <60 years: 0.06-0.90 ng/dL
60 - <65 years: 0.06-0.87 ng/dL
65 - <70 years: 0.06-0.84 ng/dL
70 - <75 years: 0.06-0.82 ng/dL
75 - <80 years: 0.06-0.79 ng/dL
80 - <85 years: 0.06-0.76 ng/dL
85 - <90 years: 0.06-0.73 ng/dL
90 - <95 years: 0.06-0.71 ng/dL
95 - 100+ years: 0.06-0.68 ng/dL
 
Females (children):
<1 year: Term infants
1 to 15 days: 0.06-0.25 ng/dL*
16 days to 1 year: values decrease gradually from newborn (0.06-0.25 ng/dL) to prepubertal levels
1-4 years: <0.04 ng/dL
5 years: <0.04-0.07 ng/dL
6 years: <0.04-0.14 ng/dL
7 years: <0.04-0.23 ng/dL
8 years: <0.04-0.34 ng/dL
9 years: <0.04-0.46 ng/dL
10 years: <0.04-0.59 ng/dL
11 years: <0.04-0.72 ng/dL
12 years: <0.04-0.84 ng/dL
13 years: <0.04-0.96 ng/dL
14 years: <0.04-1.06 ng/dL
15-18 years: <0.04-1.09 ng/dL
19 years: 0.06-1.08
 
TESTOSTERONE, BIOAVAILABLE
Males
< or =19 years: not established
20-29 years: 83-257 ng/dL
30-39 years: 72-235 ng/dL
40-49 years: 61-213 ng/dL
50-59 years: 50-190 ng/dL
60-69 years: 40-168 ng/dL
> or =70 years: not established
 
Females (non-oophorectomized)
< or =19 years: not established
20-50 years (on oral estrogen): 0.8-4.0 ng/dL
20-50 years (not on oral estrogen): 0.8-10 ng/dL
>50 years: not established
 
*Citation: J Clin Endocrinol Metab 1973;36(6):1132-1142
Interpretation
Total testosterone and general interpretation of testosterone abnormalities:
Males:
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, XX 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)
-Orchidectomy
 
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
-Cranial irradiation
-Head trauma
-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 workup 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).
 
Females:
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 (#9231 "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 overtreatment.
 
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 endpoints and the primary treatment end point is the clinical response.
 
Bioavailable and free testosterone:
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 SHBG (#9285 "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 (#80065 "Testosterone, Total and Bioavailable, Serum") or free (#8508 "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.
Outreach CPTs
CPT Modifier
(if needed)		 Quantity Description Comments
84402​ ​ ​1 ​Testosterone, bio and free ​
​84403 ​ ​1 ​Testosterone, total ​
​84410 ​ ​1 ​Bioavailable, direct measurement ​
Synonyms/Keywords
​Androgens, Bioavailable Testosterone, NonSex Hormone Binding Globulin (SHBG), Testosterone (ORDER 8533 if not specified), Testosterone Group (ORDER 8508), Testosterone, Total Only, Serum
Ordering Applications
Ordering Application Description
​Centricity ​Bioavail Testosterone, Total & Free
​Cerner None​
If the ordering application you are looking for is not listed, contact your local laboratory for assistance.
Specimen Requirements
Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)		 Pediatric Minimum Volume
(no repeat)
Serum​ ​Red Top Tube (RTT) ​3.5 mL ​2 mL ​
Collection Processing
Patient's age and sex are required.​
Specimen Stability Information
Specimen Type Temperature Time
​Serum ​ ​Refrigerated (preferred) ​14 days
​Frozen 60 days
Rejection Criteria
Gross hemolysis
​Gross lipemia
​Gross icterus ​
Useful For
Second- or third– order test for evaluating testosterone status (eg, when abnormalities of sex hormone-binding globulin are present)​
Reference Range Information
TESTOSTERONE, TOTAL
Males        
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      
Tanner Stages*                            
I (prepubertal): <7-20
II: 8-66
III: 26-800
IV: 85-1,200      
V (young adult): 300-950
 
Females           
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
Tanner Stages*
I (prepubertal): <7-20
II: <7-47
III: 17-75
IV: 20-75
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.
 
TESTOSTERONE, FREE
Males (adult):
20 - <25 years: 5.25-20.7 ng/dL
25 - <30 years: 5.05-19.8 ng/dL
30 - <35 years: 4.85-19.0 ng/dL
35 - <40 years: 4.65-18.1 ng/dL
40 - <45 years: 4.46-17.1 ng/dL
45 - <50 years: 4.26-16.4 ng/dL
50 - <55 years: 4.06-15.6 ng/dL
55 - <60 years: 3.87-14.7 ng/dL
60 - <65 years: 3.67-13.9 ng/dL
65 - <70 years: 3.47-13.0 ng/dL
70 - <75 years: 3.28-12.2 ng/dL
75 - <80 years: 3.08-11.3 ng/dL
80 - <85 years: 2.88-10.5 ng/dL
85 - <90 years: 2.69-9.61 ng/dL
90 - <95 years: 2.49-8.76 ng/dL
95 - 100+ years: 2.29-7.91 ng/dL
 
Males (children):
<1 year: Term infants
1 to 15 days: 0.20-3.10 ng/dL*
16 days to 1 year: Values decrease gradually from newborn (0.20-3.10 ng/dL) to prepubertal levels
1-8 years <0.04-0.11 ng/dL
9 years: <0.04-0.45 ng/dL
10 years: <0.04-1.26 ng/dL
11 years: <0.04-5.52 ng/dL
12 years: <0.04-9.28 ng/dL
13 years: <0.04-12.6 ng/dL
14 years: 0.48-15.3 ng/dL
15 years: 1.62-17.7 ng/dL
16 years: 2.93-19.5 ng/dL
17 years: 4.28-20.9 ng/dL
18 years: 5.40-21.8 ng/dL
19 years: 5.36-21.2 ng/dL
 
Females (adult):
20 - <25 years: 0.06-1.08 ng/dL
25 - <30 years: 0.06-1.06 ng/dL
30 - <35 years: 0.06-1.03 ng/dL
35 - <40 years: 0.06-1.00 ng/dL
40 - <45 years: 0.06-0.98 ng/dL
45 - <50 years: 0.06-0.95 ng/dL
50 - <55 years: 0.06-0.92 ng/dL
55 - <60 years: 0.06-0.90 ng/dL
60 - <65 years: 0.06-0.87 ng/dL
65 - <70 years: 0.06-0.84 ng/dL
70 - <75 years: 0.06-0.82 ng/dL
75 - <80 years: 0.06-0.79 ng/dL
80 - <85 years: 0.06-0.76 ng/dL
85 - <90 years: 0.06-0.73 ng/dL
90 - <95 years: 0.06-0.71 ng/dL
95 - 100+ years: 0.06-0.68 ng/dL
 
Females (children):
<1 year: Term infants
1 to 15 days: 0.06-0.25 ng/dL*
16 days to 1 year: values decrease gradually from newborn (0.06-0.25 ng/dL) to prepubertal levels
1-4 years: <0.04 ng/dL
5 years: <0.04-0.07 ng/dL
6 years: <0.04-0.14 ng/dL
7 years: <0.04-0.23 ng/dL
8 years: <0.04-0.34 ng/dL
9 years: <0.04-0.46 ng/dL
10 years: <0.04-0.59 ng/dL
11 years: <0.04-0.72 ng/dL
12 years: <0.04-0.84 ng/dL
13 years: <0.04-0.96 ng/dL
14 years: <0.04-1.06 ng/dL
15-18 years: <0.04-1.09 ng/dL
19 years: 0.06-1.08
 
TESTOSTERONE, BIOAVAILABLE
Males
< or =19 years: not established
20-29 years: 83-257 ng/dL
30-39 years: 72-235 ng/dL
40-49 years: 61-213 ng/dL
50-59 years: 50-190 ng/dL
60-69 years: 40-168 ng/dL
> or =70 years: not established
 
Females (non-oophorectomized)
< or =19 years: not established
20-50 years (on oral estrogen): 0.8-4.0 ng/dL
20-50 years (not on oral estrogen): 0.8-10 ng/dL
>50 years: not established
 
*Citation: J Clin Endocrinol Metab 1973;36(6):1132-1142
Interpretation
Total testosterone and general interpretation of testosterone abnormalities:
Males:
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, XX 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)
-Orchidectomy
 
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
-Cranial irradiation
-Head trauma
-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 workup 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).
 
Females:
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 (#9231 "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 overtreatment.
 
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 endpoints and the primary treatment end point is the clinical response.
 
Bioavailable and free testosterone:
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 SHBG (#9285 "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 (#80065 "Testosterone, Total and Bioavailable, Serum") or free (#8508 "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.
For more information visit:
Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
​Mayo Medical Laboratories
Testosterone, bioavailable: Monday through Friday
Testosterone, free: Monday through Saturday
Testosterone, total: Monday through Saturday​
Testosterone, bioavailable: 2 days
Testosterone, free: 3 days
Testosterone, total: 2 days​
Testosterone, bioavailable:: Differential Precipitation
Testosterone, free: Equilibrium Dialysis
Testosterone, total:: Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Reference Lab
Mayo Clinic Laboratories
For billing questions, see Contacts
Outreach CPTs
CPT Modifier
(if needed)		 Quantity Description Comments
84402​ ​ ​1 ​Testosterone, bio and free ​
​84403 ​ ​1 ​Testosterone, total ​
​84410 ​ ​1 ​Bioavailable, direct measurement ​
For most current information refer to the Marshfield Laboratory online reference manual.