Thyroid-stimulating Hormone (TSH)

CPT: 84443
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Test Details

Synonyms

  • Third-generation TSH
  • Thyrotropin

Use

Thyroid function test. Investigation of low thyroxine (T4) result; the differential diagnosis of primary hypothyroidism from normal, and the differential diagnosis of primary hypothyroidism from pituitary/hypothalamic hypothyroidism. TSH is high in primary hypothyroidism. Low TSH occurs in hyperthyroidism. Evaluation of therapy in hypothyroid patients receiving various thyroid hormone preparations: Low values are found in states of excessive thyroid replacement. Normal result on a sensitive TSH assay is acceptable evidence of adequate thyroid replacement.

Follow-up of patients who have had hyperthyroidism treated with radioiodine or surgery. Follow-up low T4 newborn results.

This third-generation TSH assay can be considered a test for thyroid disease. A result within the accepted reference interval provides strong evidence for euthyroidism.

Limitations

Spurious increase from antibovine TSH antibodies by double-antibody technique has been reported.2 TSH may be affected by glucocorticoids, dopamine, and by severe illness,3 and these remain limitations even for the new, sensitive TSH assays. TSH suppression in hypothyroidism with severe illness has been reported with TSH increase with recovery.4 Normal TSH levels in the presence of hypothyroidism have been reported with head injury.5 Iopanoic acid, ipodate, and an antiarrhythmic drug, amiodarone, cause changes in thyroid test results including increases in T4, free T4, and TSH and decreases of T3.6 TSH is not elevated in secondary hypothyroidism.

Probably no single test, even the sensitive immunoassays, can be expected to adequately reflect thyroid status under all circumstances. Among possible problems are the recovery phase of nonthyroidal illness, states of resistance to thyroid hormone, thyrotropin-producing tumors, thyroid status in acute psychiatric illness, early in thyrotoxicosis and in subacute thyroiditis.7

Methodology

Electrochemiluminescence immunoassay (ECLIA)

Reference Interval

See table.1

Age

Range (μIU/mL)

0 to 6 d

0.700−15.200

7 d to 3 m

0.720−11.000

3 m 1 d to 12 m

0.730−8.350

1 to 5 y

0.700−5.970

6 to 10 y

0.600−4.840

>10 y

0.450−4.500

Additional Information

The consequences of subclinical thyroid disease (serum TSH 0.1−0.45 μIU/mL or 4.5−10.0 μIU/mL) are minimal and current guidelines recommend against routine treatment of patients with TSH levels in these ranges, but thyroid function tests should be repeated at 6- to 12-month intervals to monitor TSH levels;8 however, treatment of subclinical hypothyroidism is indicated in patients with TSH levels >10.0 μIU/mL or in patients with TSH levels <10.0 μIU/mL in conjunction with goiter or positive for antithyroid peroxidase antibodies (or both).9 In patients who are receiving replacement therapy, the dose should be adjusted so serum TSH values range from 0.3−3.0 μIU/mL. An exception is thyroid hormone replacement treatment after thyroidectomy for differentiated thyroid cancer, in which case, a mildly to moderately suppressed TSH level is generally desirable.10 It is reasonable to consider serum TSH measurement for pregnant women or women planning to become pregnant with a family history of thyroid disease, prior thyroid dysfunction, symptoms or physical findings suggestive of hypo- or hyperthyroidism, an abnormal thyroid gland on examination, type 1 diabetes mellitus, or a personal history of autoimmune disorder.11 Suggested upper limit for the TSH reference range for pregnant women and preconception is: first trimester − <2.5 μIU/mL, and 3.0 μIU/mL in the second and third trimesters.10

Unsuspected increase in the level of serum TSH is not uncommon in elderly subjects. A study by Sawin et al found that 22 of 344 (5.9%) healthy persons older than age 60 had a TSH level >10 μIU/mL; 10 of the 22 had low T4 and FT4 index. Elderly hypothyroid individuals may have minimal recognizable clinical symptoms of thyroid deficiency.11 TSH is the single most sensitive test for primary hypothyroidism. If there is clear evidence for hypothyroidism and the TSH is not elevated, hypopituitarism should be considered (secondary hypothyroidism).

TSH levels have been elevated or inappropriately detectable for high thyroid hormone levels in some patients with thyrotropin-secreting pituitary adenomas. Delay in diagnosis of these tumors may lead to visual compromise. The effects of such neoplasms can be misdiagnosed as those of primary hyperthyroidism.

Until the late 1980s, TSH assays were not sufficiently sensitive to distinguish hyperthyroidism from euthyroid (normal) subjects. The new generation of ultrasensitive TSH immunoassays have provided a far more effective diagnostic separation of thyrotoxicosis from euthyroidism.

This assay has a sensitivity of 0.004 μIU/mL and meets all criteria as a third-generation TSH assay.

Specimen Requirements

Specimen

Serum

Volume

0.8 mL

Minimum Volume

0.3 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

Room temperature

Stability Requirements

Temperature

Period

Room temperature

14 days

Refrigerated

14 days

Frozen

14 days

Freeze/thaw cycles

Stable x3

Causes for Rejection

Citrate plasma specimen; improper labeling

Clinical Information

Special Instructions

This test may exhibit interference when sample is collected from a person who is consuming a supplement with a high dose of biotin (also termed as vitamin B7 or B8, vitamin H, or coenzyme R). It is recommended to ask all patients who may be indicated for this test about biotin supplementation. Patients should be cautioned to stop biotin consumption at least 72 hours prior to the collection of a sample.

Footnotes

  • 1. Reference Intervals for Children and Adults.Elecsys Thyroid Test. Roche Diagnostics; May 2005.8595709
  • 2. Sain A, Sham R, Singh A, et al. Erroneous thyroid-stimulating hormone radioimmunoassay results due to interfering antibovine thyroid-stimulating hormone antibodies. Am J Clin Pathol. 1979; 71(5):540-542. 377939
  • 3. Chopra IJ, Hershman JM, Pardridge MD, et al. Thyroid function in nonthyroidal illnesses. Ann Intern Med.. 1983; 98(6):946-957. 6407376
  • 4. Morley JE, Slag MF, Elson MK, et al. The interpretation of thyroid function tests in hospitalized patients. JAMA. 1983; 249(17):2377-2379. 6403725
  • 5. Slag MF, Morley JE, Elson MK, et al. Free thyroxine levels in critically ill patients. A comparison of currently available assays. JAMA. 1981; 246(23):2702-2706. 6796703
  • 6. Borst GC, Eil G, Burman KD. Euthyroid hyperthyroxinemia. Ann Intern Med. 1983; 98(3):366-378 (review). 6187257
  • 7. Ehrmann DA, Sarne DH. Serum thyrotropin and the assessment of thyroid status. Ann Intern Med. 1989; 110(3):179-181. 2643378
  • 8. Surks MI, Ortiz E, Daniels GH, et al. Subclinical thyroid disease: Scientific review and guidelines for diagnosis and management. JAMA. 2004; 291(2):228-238.14722150
  • 9. American Association of Clinical Endocrinologists medical guidelines for clinical practice for the evaluation and treatment of hyperthyroidism and hypothyroidism. Endocr Pract. 2002 Nov-Dec; 8(6):457-469.15260011
  • 10. Stagnaro-Green A, Abalovich M, Alexander E, et al. Guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and postpartum. Thyroid. 2011; 21(10):1081-1125.21787128
  • 11. Sawin CT, Chopra D, Azizi F, et al. The aging thyroid. Increased prevalence of elevated serum thyrotropin levels in the elderly. JAMA. 1979; 242(3):247-250.448912

References

Baskin HJ. Endocrinologic evaluation of impotence. South Med J. 1989; 82(4):446-449. 2495570
Brennan MD, Klee GG, Preissner CM, et al. Heterophilic serum antibodies: A cause for falsely elevated serum thyrotropin levels. Mayo Clin Proc. 1987; 62(10):894-898. 3657306
Clark PM, Clark JD, Holder R, et al. Pulsatile secretion of TSH in healthy subjects. Ann Clin Biochem. 1987; 24(Pt 5):470-476. 3310836
Cooper DS. Thyroid hormone treatment: New insights into an old therapy. JAMA. 1989; 261(18):2694-2695. 2709547
Ericsson UB, Fernlund P, Thorell JI. Evaluation of the usefulness of a sensitive immunoradiometric assay for thyroid-stimulating hormone as a first-line thyroid function test in an unselected patient population. Scand J Clin Lab Invest. 1987; 47(3):215-221. 3589485
Greenspan SL, Klibanski A, Schoenfeld D, et al. Pulsatile secretion of thyrotropin mn Man. J Clin Endocrinol Metab. 1986; 63(3):661-668. 3734036
Hamblin PS, Dyer SA, Mohr VS, et al. Relationship between thyrotropin and thyroxine changes during recovery from severe hypothyroxinemia of critical illness. J Clin Endocrinol Metab. 1986; 62(4):717-722. 3949952
Ridgway EC. Thyrotropin radioimmunoassays: Birth, life, and demise. Mayo Clin Proc. 1988; 63(10):1028-1034. 3172852
Sawin CT, Geller A, Hershman JM, et al. The aging thyroid: The use of thyroid hormone in older persons. JAMA. 1989; 261(18):2653-2655. 2709545
Surks MI, Chopra IJ, Mariash CN. American Thyroid Association guidelines for use of laboratory tests in thyroid disorders. JAMA. 1990; 263(11):1529-1532. 2308185
Watts NB. Use of a sensitive thyrotropin assay for monitoring treatment with levothyroxine. Arch Intern Med. 1989; 149(2):309-312. 2644903
Wehmann RE, Gregerman RI, Burns WH, et al. Suppression of thyrotropin in the low-thyroxine state of severe nonthyroidal illness. N Engl J Med. 1985; 312(9):546-552.3881675

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
004259 TSH 11580-8 004264 TSH uIU/mL 11580-8

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