TSH with Reflex to Free T4

The TSH with Reflex to Free T4 test contains 1 test with 1 biomarker.

TSH with Reflex to Free T4

Note that this is a Reflex test.  If initial TSH testing determines that additional testing is required, the lab will automatically charge for T4, Free #866

For patients 1 year of age or older, Free T4 will be performed at an additional charge (CPT code(s): 84439) when TSH result exceeds age/gender specific reference range.

Reference Range(s)

Premature Infants (28-36 Weeks) 

  1st Week of Life0.20-27.90 mIU/L 

Term Infants (>37 Weeks) 

  Serum or Cord Blood1.00-39.00 mIU/L 

  1-2 Days3.20-34.60 mIU/L 

  3-4 Days0.70-15.40 mIU/L

  5 Days-4 Weeks1.70-9.10 mIU/L

  1-11 Months0.80-8.20 mIU/L 

  1-19 Years0.50-4.30 mIU/L 

  ≥20 Years0.40-4.50 mIU/L


  First Trimester0.26-2.66 mIU/L 

  Second Trimester0.55-2.73 mIU/L

  Third Trimester0.43-2.91 mIU/L

TSH levels decline rapidly during the first week of life in most children, but may remain transiently elevated in a few individuals despite normal free T4 levels. For proper interpretation of an abnormal TSH from a newborn thyroid screen, a Free T4 by Dialysis (test code 35167) or Total T4 (test code 867) should be considered.

Clinical Significance

For differential diagnosis of primary, secondary, and tertiary hypothyroidism. Also useful in screening for hyperthyroidism. This assay allows adjustment of exogenous thyroxine dosage in hypothyroid patients and in patients on suppressive thyroxine therapy for thyroid neoplasia.

Alternative Name(s) 

Thyroid Stimulating Hormone with Reflex

The following is a list of what is included in the item above. Click the test(s) below to view what biomarkers are measured along with an explanation of what the biomarker is measuring.

Also known as: Thyroid Stimulating Hormone with Reflex To FT4 , TSH WReflex To Ft4

TSH W/Reflex To Ft4

*Process times are an estimate and are not guaranteed. The lab may need additional time due to weather, holidays, confirmation/repeat testing, or equipment maintenance.

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