Accessibility

Labcorp and its Specialty Testing Group, a fully integrated portfolio of specialty and esoteric testing laboratories.

Thyroxine-binding Globulin (TBG), Serum

CPT: 84442
Print Share

Expected Turnaround Time

1 - 3 days



Related Documents

For more information, please view the literature below.

Thyroid Testing: Assessing Thyroid Disease in Your Patients


Specimen Requirements


Specimen

Serum


Volume

0.8 mL


Minimum Volume

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


Container

Red-top tube or gel-barrier tube


Collection

If a red-top tube is used, transfer separated serum to a plastic transport tube.


Storage Instructions

Refrigerate


Stability Requirements

Temperature

Period

Room temperature

7 days

Refrigerated

14 days

Frozen

14 days

Freeze/thaw cycles

Stable x3


Causes for Rejection

Gross hemolysis


Test Details


Use

Distinguish between high T4 levels due to hyperthyroidism and due to increased binding by TBG in euthyroid individuals who have normal levels of free hormones; document cases of hereditary deficiency or increase of TBG; work-up of thyroid disease. In patients with low T4, high T3 (uptake) or the reverse, who clinically seem eumetabolic and have normal FTI, measurement of TBG is only occasionally needed. Some such patients may have hereditary anomalies of TBG. TBG is increased by estrogens, tamoxifen, pregnancy, perphenazine, and in some cases of liver disease, including hepatitis. Decreased TBG is found with some instances of chronic liver disease, nephrosis and systemic disease, and with large amounts of glucocorticoids, androgens/anabolic steroids, and acromegaly. Although alterations of TBG are usually resolved by the thyroid profile, TBG must occasionally be directly measured.

Kindreds are described with elevated TBG and hyperthyroxinemia as a harmless genetic abnormality. They have normal levels of TSH and free T4 and decreased T3 uptake.2 Structural variants of TBG are inherited as X-chromosome-linked traits, most inherited structural abnormalities in TBG cause decreased affinity for thyroid hormone.3


Limitations

TBG is normal in familial dysalbuminemic hyperthyroxinemia, an entity which can be incorrectly identified as thyrotoxicosis.4 Triiodothyronine uptake was described as having produced information equivalent to TBG in a study of 372 subjects.5


Methodology

Immunochemiluminometric assay (ICMA)


Reference Interval

See table.1

Age

Male (μg/mL)

Female (μg/mL)

1 to 11 m

16−33

18−32

1 to 3 y

16−32

19−34

4 to 6 y

17−30

18−31

7 to 12 y

17−29

15−29

13 to 18 y

13−26

14−29

>18 y

13−39

13−39


Footnotes

1. Hicks JM, Godwin ID, Beatey J, Bailey J, Bjorn S, Soldin SJ. Pediatric reference ranges for thyroid binding globulin. Clin Chem. 1993; 39:1172. Poster 248
2. Viscardi RM, Shea M, Sriwantanakul K, McCormick K. Hyperthyroxinemia in newborns due to excess thyroxine-binding globulin. N Engl J Med. 1983 Oct 13; 309(15):897-899. 6412142
3. Sarne DH, Refetoff S, Nelson JC, Linarelli LG. A new inherited abnormality of thyroxine-binding globulin (TBG-San Diego) with decreased affinity for thyroxine and tri-iodothyronine. J Clin Endocrinol Metab. 1989 Jan; 68(1):114-119. 2491856
4. Ruiz M, Rajatanavin R, Young RA, et al. Familial dysalbuminemic hyperthyroxinemia: A syndrome that can be confused with thyrotoxicosis. N Engl J Med. 1982 Mar 18; 306(11):635-639. 6173750
5. Wilke TJ. Free thyroid hormone index, thyroid hormone/thyroxine-binding globulin ratio, tri-iodothyronine uptake, and thyroxine-binding globulin compared for diagnostic value regarding thyroid function. Clin Chem. 1983 Jan; 29(1):74-79.6401235

References

Borst GC, Eil C, Burman KD. Euthyroid hyperthyroxinemia. Ann Intern Med. 1983 Mar; 98(3):366-378 (review). 6187257
Ingbar SH. Diseases of the thyroid. In: Braunwald E, Isselbacher KJ, Petersdorf RG, et al, eds. Harrison's Principles of Internal Medicine. 11th ed. New York, NY: McGraw-Hill;1987: 1732-1752.
Nelson JC, Tomei RT. Dependence of the thyroxine/thyroxine-binding globulin (TBG) ratio and the free thyroxine index on TBG concentrations. Clin Chem. 1989 Apr; 35(4):541-544. 2495196
Oberkotter LV, Farber M. Thyroxine-binding globulin in serum and milk specimens from puerperal lactating women. Obstet Gynecol. 1984; 64(2):244-247. 6429594
Refetoff S. Inherited thyroxine-binding globulin abnormalities in man. Endocr Rev. 1989 Aug; 10(3):275-293.2506004

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
001735 Thyroxine Binding Globulin 3021-3 001735 Thyroxine Binding Globulin ug/mL 3021-3

For Providers

Please login to order a test

Order a Test

© 2021 Laboratory Corporation of America® Holdings and Lexi-Comp Inc. All Rights Reserved.

CPT Statement/Profile Statement

The LOINC® codes are copyright © 1994-2021, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee. Permission is granted in perpetuity, without payment of license fees or royalties, to use, copy, or distribute the LOINC® codes for any commercial or non-commercial purpose, subject to the terms under the license agreement found at https://loinc.org/license/. Additional information regarding LOINC® codes can be found at LOINC.org, including the LOINC Manual, which can be downloaded at LOINC.org/downloads/files/LOINCManual.pdf