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HelpTest Code STSH Thyroid-Stimulating Hormone-Sensitive (s-TSH), Serum
Testing Algorithm
See Thyroid Function Ordering Algorithm in Special Instructions.
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
SerumOrdering Guidance
This is a standalone test for sensitive thyrotropin (s-TSH; formerly thyroid-stimulating hormone).
If a cascade approach is preferred, order THSCM / Thyroid Function Cascade, Serum, which utilizes a cascaded testing procedure to efficiently evaluate and monitor functional thyroid status. Serum s-TSH is the first-line test and when the s-TSH result is abnormal, appropriate follow-up tests will automatically be performed.
Specimen Required
Collection Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Submission Container/Tube: Plastic vial
Specimen Volume: 0.6 mL
Collection Instructions:
1. Serum gel tubes should be centrifuged within 2 hours of collection.
2. Red-top tubes should be centrifuged, and the serum aliquoted into a plastic vial within 2 hours of collection.
Specimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum | Refrigerated (preferred) | 7 days |
| Frozen | 30 days | |
| Ambient | 7 days |
Reference Values
0-5 days: 0.7-15.2 mIU/L
6 days-2 months: 0.7-11.0 mIU/L
3-11 months: 0.7-8.4 mIU/L
1-5 years: 0.7-6.0 mIU/L
6-10 years: 0.6-4.8 mIU/L
11-19 years: 0.5-4.3 mIU/L
≥20 years: 0.3-4.2 mIU/L
For SI unit Reference Values, see https://www.mayocliniclabs.com/order-tests/si-unit-conversion.html
Day(s) Performed
Monday through Sunday
CPT Code Information
84443
Clinical Information
Thyrotropin (TSH, formerly thyroid-stimulating hormone) is a glycoprotein hormone consisting of 2 subunits. The alpha subunit is similar to those of follicle-stimulating hormone, human chorionic gonadotropin, and luteinizing hormone. The beta subunit is different from those of the other glycoprotein hormones and confers its biochemical specificity.
TSH is synthesized and secreted by the anterior pituitary in response to a negative feedback mechanism involving concentrations of free triiodothyronine and free thyroxine. Additionally, the hypothalamic tripeptide, thyrotropin-releasing hormone, directly stimulates TSH production.
TSH interacts with specific cell receptors on the thyroid cell surface and gives rise to 2 main actions. First, it stimulates cell reproduction and hypertrophy. Second, it stimulates the thyroid gland to synthesize and secrete triiodothyronine and thyroxine.
Serum TSH concentrations exhibit a diurnal variation with the peak occurring during the night and the nadir occurring between 10 a.m. and 4 p.m. This biological variation does not influence the interpretation of the test result since most clinical TSH measurements are performed on ambulatory patients between 8 a.m. and 6 p.m.
When hypothalamic-pituitary function is normal, a log/linear inverse relationship between serum TSH and free thyroxine exists.
See Thyroid Function Ordering Algorithm in Special Instructions.
Report Available
Same day/1 to 2 daysReject Due To
| Gross hemolysis | Reject |
| Gross lipemia | OK |
| Gross icterus | OK |
Method Name
Electrochemiluminescent Immunoassay
Forms
If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.