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TRHLO
TRH, LONG, TSH STIMULATION WITH TRH (THYROID RELEASING HORMONE), SERUM

Test Code TRHLO 
Test TRH, LONG, TSH STIMULATION WITH TRH (THYROID RELEASING HORMONE), SERUM 
Methodology Electrochemiluminescence Immunoassay (ECLIA) 
Description Useful for the diagnosis of hyperthyroidism and its cause, ie. Primary (thyroid) , secondary (pituitary), or tertiary (hypothalamus), or to assess TSH production in suspected pituitary or hypothalamic disease. Test includes four TSH and one T4 determinations.

NOTE: This test, when ordered on Medicare patients, is subject to the National Coverage Determination (NCD) policy "Thyroid Testing". Please verify that the diagnosis code (ICD-9) you have chosen demonstrates medical necessity for the test as documented in the physician's patient record. The CMS web site or the NorDx Limited Coverage Documentation Guide are available to assist you with this verification. A properly executed Advance Beneficiary Notice (ABN) must be submitted with the specimen if medical necessity is not demonstrated by the ICD-9 code chosen. 

Specimen Draw blood in either a plain, red-top tube or SST ® tube for a baseline TSH and T4 determination and TSH determinations at 30,45,and 60 minutes post TRH (Relefact®) injection. Label all tubes with time drawn. Spin down and send 1.0 mL (minimum volume: 0.5 mL) of serum refrigerated for each draw. 
Reference Values Generally TSH levels peak 20 - 40 minutes after TRH (Relefact®) injection with levels varying somewhat with age. Peak levels correlate with baseline TSH concentrations in hyperthyroidism. An absent response supports a pituitary defect. An augmented response suggests primary hypothyroidism. 
Analytic Time 1 Day 
Day(s) Test Set Up Monday through Sunday 
CPT Code(s) 80438 x 3  TSH (30,45 & 60 minutes)
84436  T4 (baseline)
84443  Baseline TSH