Thyroid-stimulating Hormone (TSH) in Pregnancy

CPT: 84443
Updated on 11/17/2018
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Test Details

Synonyms

  • Thyrotropin in Pregnancy

Use

Assessment of thyroid function during pregnancy

Methodology

Electrochemiluminescence Immunoassay (ECLIA)

Reference Interval

Pregnancy:

• First trimester: 0.100−2.500

• Second trimester: 0.200−3.000

• Third trimester: 0.300−3.000

• Nonpregnant adult: 0.450−4.500

Additional Information

Thyroid function test results of healthy pregnant women differ from those of healthy nonpregnant women. Following conception, circulating total T4 (TT4) and T4-binding globulin (TBG) concentrations increase by six to eight weeks and remain high during delivery. Thyrotrophic activity of hCG results in a decrease in serum TSH in the first trimester. During pregnancy, therefore, women have lower serum TSH concentrations than before pregnancy. Serum TSH and its reference range gradually rise in the second and third trimesters, but it is noteworthy that the TSH reference interval remains lower than in nonpregnant women. In a small percentage of women, TSH can be very suppressed (<0.01 mIU/mL) and yet still represent a normal pregnancy. There are slight but significant ethnic differences in serum TSH concentrations. Black and Asian women have TSH values that are on average 0.4 mIU/mL lower than in white women; these differences persist during pregnancy.1 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 red-top tube is used, transfer separated serum to a plastic transport tube.

Storage Instructions

Room temperature. Stable at room temperature, refrigerated, or frozen for 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.

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
004593 TSH Pregnancy 11580-8 004591 TSH Pregnancy uIU/mL 11580-8

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