Testosterone, Free, Mass Spectrometry/Equilibrium Dialysis (Endocrine Sciences)

CPT: 84402; 84403
Updated on 1/11/2019
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Test Details

Use

Free testosterone is the fraction of total testosterone that is not bound to circulating proteins. The free fraction is available to diffuse into target cells to interact with receptors or enzymes. The concentration of free testosterone is low relative to total testosterone, typically <3% of the total testosterone concentration. Total circulating testosterone is bound to sex hormone-binding globulin (SHBG) or albumin. Measurement of total and free testosterone is key in diagnosis of androgen excess or deficiency. Free testosterone is best measured by equilibrium dialysis, while total testosterone is measured by HPLC with tandem mass spectrometry.1-3 Free testosterone is estimated in this profile using these recommended techniques.

Tritiated testosterone is added to the sample and allowed to dialyze across a membrane. Once equilibrium has been achieved, the solutions on both sides of the membrane are sampled to determine the percent free testosterone. Total testosterone is measured by HPLC with tandem mass spectrometry. Serum free testosterone is then calculated by multiplying the percent free testosterone by the total testosterone concentration with unit correction.

Limitations

This method is recommended for testing women, children, and hypogonadal men.

Methodology

Testosterone: high-pressure liquid chromatography (HPLC)/tandem mass spectrometry; free testosterone: equilibrium dialysis

Reference Interval

See tables.

Testosterone Expected Values

Age

Male (ng/dL)

Female (ng/dL)

Premature Infants

26 to 28 wk, day 4

59−125

5−16

31 to 35 wk, day 4

37−198

5−22

Full-term Infants

Newborns, 1 to 7 m

75−400

20−64

Prepubertal Children

1 to 10 y

<2.5−10

1 to 9 y

<2.5-10

Adults

>18 y

264−916

Premenopausal

10−55

Postmenopausal

7−40

Tanner Stage - Pubertal Ages

Tanner Stage

Male

Female

Age (y)

Testosterone (ng/dL)

Age (y)

Testosterone (ng/dL)

I

<9.8

<2.5−10

<9.2

<2.5−10

II

9.8−14.5

18−150

9.2−13.7

7−28

III

10.7−15.4

100−320

10.0−14.4

15−35

IV

11.8−16.2

200−620

10.7−15.6

13−32

V

12.8−17.3

350−970

11.8−18.6

20−38

Free Testosterone Expected Values

Age

Male

Female

% Free

pg/mL

% Free

pg/mL

Full-term Infants

1 to 15 d

0.9−1.7

1.5−31

0.8−1.5

0.5−2.5

1 to 2 m

0.4−0.8

3.3−18

0.4−1.1

0.1−1.3

3 to 4 m

0.4−1.1

0.7−14

0.5−1.0

0.3−1.1

5 to 6 m

0.4−1.0

0.4−4.8

0.5−0.8

0.2−0.6

Prepubertal Children

1 to 10 y

0.4−0.9

0.15−0.6

Same as males

Puberty: Comprehensive values for free testosterone by dialysis for both males and females throughout puberty are currently unavailable.

Male

Female

% Free

pg/mL

% Free

pg/mL

Adults

1.5−3.2

52−280

0.8−1.4

1.1−6.3

See tables.

Testosterone Expected Values

Age

Male (ng/dL)

Female (ng/dL)

Premature Infants

*Male: Levels decrease rapidly during the first week to 20−50 ng/dL, then increase to 60−400 ng/dL (mean = 190) between 20−60 days. Levels then decline to a prepubertal range <2.5−10 ng/dL by seven months.

*Female: Levels decrease during the first month to <10 ng/dL and remain there until puberty.

26 to 28 wk, day 4

59−125

5−16

31 to 35 wk, day 4

37−198

5−22

Full-term Infants*

Newborns, 1 to 7 m

75−400

20−64

Prepubertal Children

1 to 10 y

<2.5−10

Adults

>18 y

350−1030

Premenopausal

10−55

Postmenopausal

7−40

Tanner Stage - Pubertal Ages

Tanner Stage

Male

Female

Age (y)

Testosterone (ng/dL)

Age (y)

Testosterone (ng/dL)

I

<9.8

<2.5−10

<9.2

<2.5−10

II

9.8−14.5

18−150

9.2−13.7

7−28

III

10.7−15.4

100−320

10.0−14.4

15−35

IV

11.8−16.2

200−620

10.7−15.6

13−32

V

12.8−17.3

350−970

11.8−18.6

20−38

Free Testosterone Expected Values

Age

Male

Female

% Free

pg/mL

% Free

pg/mL

Full-term Infants

1 to 15 d

0.9−1.7

1.5−31

0.8−1.5

0.5−2.5

1 to 2 m

0.4−0.8

3.3−18

0.4−1.1

0.1−1.3

3 to 4 m

0.4−1.1

0.7−14

0.5−1.0

0.3−1.1

5 to 6 m

0.4−1.0

0.4−4.8

0.5−0.8

0.2−0.6

Prepubertal Children

1 to 10 y

0.4−0.9

0.15−0.6

Same as males

Puberty: Comprehensive values for free testosterone by dialysis for both males and females throughout puberty are currently unavailable.

Male

Female

>

% Free

pg/mL

% Free

pg/mL

Adults

1.5−3.2

52−280

0.8−1.4

1.1−6.3

See tables.

Testosterone Expected Values

Age

Male (ng/dL)

Female (ng/dL)

Premature Infants

26 to 28 wk, day 4

59−125

5−16

31 to 35 wk, day 4

37−198

5−22

Full-term Infants

Newborns, 1 to 7 m

75−400

20−64

Prepubertal Children

1 to 10 y

<2.5−10

1 to 9 y

<2.5-10

Adults

>18 y

264−916

Premenopausal

10−55

Postmenopausal

7−40

Tanner Stage - Pubertal Ages

Tanner Stage

Male

Female

Age (y)

Testosterone (ng/dL)

Age (y)

Testosterone (ng/dL)

I

<9.8

<2.5−10

<9.2

<2.5−10

II

9.8−14.5

18−150

9.2−13.7

7−28

III

10.7−15.4

100−320

10.0−14.4

15−35

IV

11.8−16.2

200−620

10.7−15.6

13−32

V

12.8−17.3

350−970

11.8−18.6

20−38

Free Testosterone Expected Values

Age

Male

Female

% Free

pg/mL

% Free

pg/mL

Full-term Infants

1 to 15 d

0.9−1.7

1.5−31

0.8−1.5

0.5−2.5

1 to 2 m

0.4−0.8

3.3−18

0.4−1.1

0.1−1.3

3 to 4 m

0.4−1.1

0.7−14

0.5−1.0

0.3−1.1

5 to 6 m

0.4−1.0

0.4−4.8

0.5−0.8

0.2−0.6

Prepubertal Children

1 to 10 y

0.4−0.9

0.15−0.6

Same as males

Puberty: Comprehensive values for free testosterone by dialysis for both males and females throughout puberty are currently unavailable.

Male

Female

>

% Free

pg/mL

% Free

pg/mL

Adults

1.5−3.2

52−280

0.8−1.4

1.1−6.3

Specimen Requirements

Specimen

Serum, frozen

Volume

2 mL

Minimum Volume

1 mL (Note: This volume does not allow for repeat testing.)

Container

Gel-barrier tube or red-top tube

Collection

Serum must be separated from cells within 45 minutes of venipuncture. Send serum in a plastic transport tube. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.

Storage Instructions

Freeze

Stability Requirements

Temperature

Period

Room temperature

6 days

Refrigerated

7 days

Frozen

2.6 years

Freeze/thaw cycles

Stable x9

Causes for Rejection

EDTA plasma; citrated plasma; hemolysis >5%

Clinical Information

Special Instructions

This method is recommended for testing women, children, and hypogonadal men.

Footnotes

1. Rosner W, Auchus RJ, Azziz R, Sluss PM, Raff H. Utility, limitations, and pitfalls in measuring testosterone: An Endocrine Society position statement. J Clin Endocrinol Metab. 2007 Feb; 92(2):405-413. 17090633
2. Fritz KS, McKean AJ, Nelson JC, Wilcox RB. Analog-based free testosterone test results linked to total testosterone concentrations, not free testosterone concentrations. Clin Chem. 2008 Mar; 54(3): 512-516. 18171714
3. Miller KK, Rosner W, Lee H, et al. Measurement of free testosterone in normal women and women with androgen deficiency: Comparison of methods. J Clin Endocrinol Metab. 2004 Feb; 89(2):525-533. 14764757

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
500726 Testosterone Free MS/Dialysis 500160 Testosterone, Total ng/dL 2986-8
500726 Testosterone Free MS/Dialysis 500727 % Free Testosterone (Dialysis) % 15432-8
500726 Testosterone Free MS/Dialysis 500728 Free Testosterone, Serum pg/mL 2991-8

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